Restorations are the most underpowered Mecha Upgrades in the core rules. While I believe the expansion's Restoration Powers did a more than adequate job buffing them, I'd like to go over how and why their core-only versions ended up the way they are. Let's start with something that will probably explain a lot: I don't like healing-type abilities in RPGs. I say this not as a player (I've always liked to play support), but as a designer.
Here's the thing about healing in combat-centric games: It doesn't do anything, it undoes what other people did. It doesn't win the game, it helps you not lose. And as such, it is either not worth doing or worth doing because it heals faster than other people can hurt you. Few things are as frustrating as managing to hurt your enemy only to watch them heal up the damage. It just isn't fun to be on the other side of.
This is not to say I didn't want to have any healing abilities at all, or that I wanted to make them bad. It is just that, in case of doubt whether something is too weak or too strong, I erred on the side of making healing abilities weaker rather than stronger. If I make a mistake balancing weapons or offensive buffs, combat is too fast and rocket-taggy, which is bad but manageable. If I make a mistake balancing heals or defensive buffs, combat is a slow grind that takes forever, which I think is a much worse problem. Consider that BCG is a game where everything available to PCs is also available to NPCs, and my position becomes easier to understand. I don't expect people to agree with all of this, but I wanted to make my position clear.
Anyway, Restoration Upgrades: I wanted to prevent potentially infinite healing and the Systems stat seemed like the most logical existing variable for the number of times you could use the Upgrades. I immediately realized that PCs who wanted to use these Upgrades would be the ones maxing Systems, rather than the ones keeping it at an average value. Restorations had to be balanced at 7 Systems and above, rather than between 4 and 6 which is what other Upgrades were balanced against. Again, I was being way too conservative about them. Let's go over the three of them:
This was the first Restoration Upgrade designed. I had the basic idea of the Restorations system down, so to figure out what the basic healing Upgrade would do, I looked at Absolute Barrier. Healing is better than damage prevention, so I figured using a similar formula to Absolute Barrier's, but weaker, would work out alright. It wasn't terrible, but it wasn't great either. The real problem was when many of the weaker weapons in the game got buffed, that was when keeping up with the damage output of NPCs got very hard.
If Jury Rig's problem was that it had to be a weaker Absolute Barrier, Regenerative's problem was that it had to be a weaker Jury Rig. At first, this Upgrade healed HALF the amount of Energy spent on it, which, as you can imagine, is kind of terrible. Now it uses two Restorations instead of one and restores the same amount of Threshold Jury Rig does. The end result is... That this is pretty much just a worse Absolute Barrier. At least Jury Rig can heal other PCs who don't have all the Energy to spare. Not a fan.
Probably the strongest of these three, if only because it didn't need a Genre Power to make it useable. The best use for Resupply is to restore your own Support Upgrades so you can keep comboing them. The most common Support Upgrades are the cheap ones that can be used reliably without spending them first, but comboing the expensive Supports is very strong and Resupply is worth considering for a more debuff-oriented Support build.
So, in hindsight, the problem with Jury Rig and Regenerative is that they were designed as an Absolute Barrier variant. Had they used a different number for their healing value, like a static 5 or just the user's systems, they would have turned out more useful. A change like this would need both Upgrades to have less uses though. The total uses available to each PC would need to be half Systems or equal to Power Level or something like that. That would have also likely meant a buff for Resupply, likely just making it not use an action. Also, they probably would be internal upgrades rather than external upgrades.
Again, the expansion largely fixes the problems with both Jury Rig and Regenerative with the addition of Restoration Powers. Without it, both Upgrades essentially need you to have a way to stop taking damage while you heal in peace, such as having everybody temporarily hide behind a Guardian of Steel or short pauses between battles or something like that.
Next: Mobility Upgrades.