General Upgrades can be divided into two categories. A few grant simple benefits that can be very useful if you have the spare MP for them, but most are very specific abilities that require you to plan a character build around them. They're all Internal, and thus can't be disabled, the former because it wouldn't make sense for your Mecha to lose those abilities and the latter because that would completely ruin your character if you lost that. They're a hodgepodge of assorted abilities so it's more interesting to talk about them individually than as a whole.
Commander Type + Early Warning and Control
Support Upgrades are very strong buffs or debuffs but also they're rarely worth your entire Turn, especially if they are also spent on use. Commander Type was designed from the ground up to be the thing that pushed Support builds to playability. The Upgrade went through several versions, at one point it allowed multiple Support activations each turn and at another it also had an Early Warning and Control effect... For all Support Upgrades, not just the ones that cost 5. One Actionless Support each Turn with replenishing the cheaper Supports was the right effect, but it was a bit too wordy for a single General Upgrade - and it was also hard to purchase early since it was so expensive at 20 MP. The Actionless activation and replenishing abilities were split into two Upgrades and that's how both of them came to be.
As for how they worked out, Supports had to be buffed several times before Support builds were competitive with other specialists. Even then, they do suffer from being a little too expensive to function efficiently at low Power Levels. The expansion gave them enough new toys that I believe this is no longer an issue. I'll go more into detail when we get to the Support Upgrades section.
The name should probably be different, considering this is an ability that doesn't really have much to do with Support Upgrades. Other than that, it is a very simple and useful Upgrade that lets the user avoid friendly fire. It's fundamental for artillery builds and games full of solo Boss battles. It doesn't really make the user more powerful, it just keeps them from potentially killing their allies, so it is a very cheap Upgrade to encourage people to take it.
This was once a Mobility Upgrade, much like Reversible Thrusters, but at a 5 MP Cost. It didn't make much sense as a thing that could be Maimed though, and at 5 MP you could buy as an afterthought to ignore the most common forms of movement denial. The result was that, after the first few Power Levels, nearly everyone had it. That was a little too good, so it became an Internal Upgrade for 10 MP instead, so it's much rarer but also harder to deal with since it can't be disabled.
Stealth Field + Guardian of Steel
These two used to be a single Upgrade in Stealth Field. The game needed something to represent cloaking tech, but invisibility is not just an extremely powerful ability but also logically a very weird thing to give to a giant robot. It had to be a purely defensive ability and those are hard to make both interesting and efficient to use without accidentally making someone invincible.
The original Stealth Field had a range greater than 1 so it could cloak allies with its absurd tech. It was extremely overpowered and it took separating its effects into two Upgrades plus reducing the range of Guardian of Steel to the very minimum in order to keep it balanced. Even then, NPCs with it often turn into puzzle encounters of a sort, forcing the PC Squad to find a workaround around it. Stealth Field ended up very weak without its companion Guardian of Steel, but it is still worth taking for Components to make Combiners even more invincible when Maneuvering. It took some effort but I think both abilities turned out alright.
This originally only gave an Advantage to Blast type Weapons but made the Blast area much larger. It was extremely powerful against Grunt mobs but very underpowered the rest of the time and actively a hindrance without Expert Support. It was too extreme, so the Blast radius bonus got toned down (as did many of the Blast sizes of individual Weapons) and then made compatible with Line and Burst Weapons. It is still a very all-or-nothing Upgrade, but it's cheaper than most other weapon specializations and doesn't automatically make your party hate you, so it's about as good as it gets for its concept.
I knew that I wanted Subpilot PCs to be allowed to use only Utility actions. This would let them Maneuver, Support and Boost or Disengage which should be enough to cover any situation. The problem with this decision was that then Subpilot NPCs would be extremely powerful, there's no way we could allow a PC to essentially buy 2 actions for every Turn. So we were going to need separate rules for PC and NPC Subpilots. The question was, how do we represent having another Character? We already had Commander Type for Supports, Mobility Upgrades for extra movement, and Maneuvering was out of the question. The other thing that PCs had to contribute other than their Actions were their Genre Points and Genre Powers, so we tried Assistant as just one of each at 10 MP and it was a little too good. After changing it to 15 MP it was still worth taking but not too good to not take it, so it stayed that way. I believe this is the right way to do Subpilot NPCs.
Duelist Model + Sniper Model
Originally there was a single Upgrade that had you choose between Melee and Shooting, giving you an Advantage to using that Weapon type. It was split into two different Upgrades with some additional bonuses. Duelist Model makes you decent at forcing enemies to focus on you, while Sniper Model lets you shoot from very far away. Sniper Model had some additional conditions to making it work - the Range bonus only applies to Weapons with the Long Range ability and the Advantage doesn't work at Range 0 - because at the time Shooting Weapons were generally stronger than Melee ones. Now that the Expansion has done more to balance Melee with Shooting, I think at least the Advantage clause could go away. But at the time it was a necessary matter for game balance.
Integrated Weapons + Invincible Alloy
Unlike the previous double entries, these weren't a single Upgrade that got split into two during development. I'm combining them so I can talk about Antimaims in a general sense instead. As I explained last week, Maims do wacky things to game balance and tend to skew combat towards who can Maim the other first, so I wanted to have a couple of Upgrades in the game to mitigate their effects. Playtesting showed that they weren't just useful, they were obligatory in order to keep Power Level 3+ combat fun, so there was a lot of pressure on getting them right.
Balancing these two (and the Expansion Pack a few pages later) with each other was hard. They were the abilities that got tweaked and rewritten the most in the core book, because they didn't just need to be balanced in a vacuum, they had to be balanced in the context of the builds each one slotted well into. Integrated Weapons had to cost just enough to keep Beam specialists from having too much raw attack power and Invincible Alloy had to give Duelists the extra survivability they needed to keep the Enemy focused on them. Your ability to use one of the available Antimaims in the game was a huge factor to how good your build was. They didn't cover all possible builds effectively in core, but BCZ added juuust enough more Antimaims to make up for that.
This is the weapon specialization upgrade with the most raw power vs single targets. Beam weapons were always powerful and this made them even stronger, so we had to be careful with it. It's expensive, and Beam Weapons already have an extra MP cost in Energy, which is their main balancing factor. The other balancing factor is that, if you go all in on Beam weapons, you need to find the ones with the right abilities and Energy. It's relatively tricky and the extra vulnerability to Energy debuffs keeps it in check. Overall, I'd say this one is fine.
We'll leave this one for later, when we get to the Transformation Upgrade.
The coolest and most badass of all the General Upgrades. Originally this didn't nullify the base Disadvantage from using Default Weapons, nor did it allow the user to punch through barriers. Both of those came through as a result of playtesting showing that 1-2 Advantages with no other secondary abilities was not enough to build around. The addition gives PCs a higher Damage ceiling without making the base attack power of Default Weapons too much higher. It's one of the builds with the most raw power and the easiest to play effectively, nearly every PC Squad I've seen has one person using The Beast, so I'm going to assume everybody else likes it as much as I do.
Next: Active Defenses.