Regeneration of SP

[Handsome Jack]

The can of worms that I see with the HP for SP trade would be the potential abuse that would have to be balanced: in fights, damage does not give you penalty points, but spent SP gives you bonuses. Assuming that no balancing methods are implemented on either "end" of this, a user could burn SP on a Power-Up + Super Move, then damage themselves to regenerate the SP and spend them again. A high-level character with T3s could accumulate a lot of bonus points that way.

Balancing could be done maybe by capping the bonus points in a fight to [points] x [user's level]? So a level 5 character could only get up to 5 bonus points, as they have 5 SP. If they regenerate some to throw more Super Moves than 5 SP would get them, it's counted as fluff.

Even at the double HP cost per SP gained, using Tier 3s will probably kill you in your example. 1 Round of T3 Power-Up costs 6 SP, which would burn 12 HP. With a cap of 20 HP, you do literally only do that once. At lower levels of Power-Ups and Super Moves, it becomes more viable for sure (allowing one to maintain a T1 Power-Up through 3 rounds of a fight for 12 HP). But we would certainly need to make lost HP an actual detriment in a fight for sure. At the moment, HP loss only really seems to come up during large scale storylines, which makes me agree that, for now, it'd be an unbalanced Power. 

What about Elixirs? They're Consumables that give SP.

But if it's a Power you need I'd agree with Ammy about the cap, or more simply, limits on how many times you can use this power. Like, you can only use Recharge three times or something.

This is true. But in the same vein of their being items which act like Power-Ups and the Regeneration Power, I felt there could be a Power that would replicate the effects of a Item, obviously at some cost.

It would be a real can of worms to open, because it would basically allow you to go beyond your normal level and then we'd have to think about that when balancing costs. Furthermore, since Healing scales, giving more Damage per SP as your Defense increases, it introduces a scaling problem where you'd paradoxically have to increase the HP cost to keep it balanced with Healing, or else create an ability that's much more useful for lower levels than it is higher levels.

At the end of the day, we'd probably have to have it so limited that it would be more detrimental than beneficial to even use it in the first place.

Perhaps it wouldn't be so bad to keep it as a Power that helps out more during lower-levels? You've always said that this system was designed so even a level 1 character could theoretically beat, say, Proto Man, with enough skill. With SP spent adding points to a grading, those at a higher level have a significant advantage over those at a lower level. For example, a level 27 character could, theoretically use a Tier 3 Power-Up and a Tier 3 Super Move every Round and add 27 points to their score (assuming SP spent equals 1 point added to score). Even assuming the level 1 character pulls off some Stephen King level writing and the level 27 writes 1 word a post, it'd be an impossible gap to surpass.

SP is one of the weirder things to work in mechanics for, because unlike everything else, it actually improves as you Level Up (not really counting simply unlocking new abilities here or things you spend OM on, just passive increases in power). Putting limits on how much you can regain based on character-level would be one way of skewing it back towards the higher level characters. At the same time, eventually the power would become useless to the high level character anyway, as his or her SP begins to exceed the amount they could possibly expend in a standard combat. My suggestion would be to just make Damage actually matter in a fight. Even if this Power never gets approved, it'll still be a good thing to do to allow a string of low-level folks to slowly wear down a massive threat.