For Resupply, I'd compare with hit points. Regeneration of hp vs reactors for energy are at equal strength, though reactor is more available. Guts is 30 SP and Faith is 40 SP. Also, you don't die from having zero energy but you do if your hp drops to zero so hp so the value of energy vs hp feels difficult to assess.
I agree that it is a good limiter for powerful abilities but usually the greatest limiter of power is action-economy.
Zeal is 70 SP for a lot of extra power, so how much would an energy equivalent of Guts/Faith be?
Thing is that you want your energy-recovering spirit to restore two mechas's supply. That's not how it worked on the game, not how the other spirits here work, and just restoring energy would be good.
Also trivia, I had considered making it myself when making the first spirit list, but then decided it would be a bit silly somehow willing somebody else's weapon to have more bullets, but after watching knights of Sidonia I guess I can go with "improvise something else as ammo".
Charge/Vigor Morale spirits: Yep. As I mentioned you already replaced Morale for some feats so I'm not sure about bringing a Morale system over this without the feats having to be done over.
Yeah, between mechas and spirits I believed there were already more than enough subsystems for this.
Good one for Taunt/Exhaust!
There's a reason why I have this avatar, you know?
I was also considering adding Mercy (10), which leaves an enemy close to death when it should die. For Dnd though perhaps it would translate better to dealing nonlethal damage or otherwise leaving a mecha disabled but not destroyed.
Fine, go ahead and make your defeat without destruction spirit.
More trivia, Mercy in the SRW games is more of a situational ability since there's at least always one mission where you need to reduce your target's HP to critical without killing them (usually because they have nukes, or are nukes, and killing them would mean everybody died).
Also considering:
Direct Attack (30) : Your next attack, if it hits, passes through
whatever defenses the opponent has, including Support Defenses and
any sort of barrier. It hits the enemy directly.
Would probably work better if you specified more, like "ignores defensive abilities with Barrier/Shield/Whatever on its name."
As for Hope, that's exactly what it did in the game. Was that spirit regeneration loop a thing or was it just not worth it considering who had access to it?
O'rrly?
Lefina has something to say about that. Hope only recovered one ally's worth of SP. There's no two-target spirits in any SWR as far as I'm aware.
There was a possible loophole with another character that had Hope for just 50 SP, so if you got her the spirit-reduction "feat", she would become an infinite spirit battery. However you only unlocked said character very late in the game, thus you would need to grind multiple Newgame+ to get it done.
Otherwise I'm also thinking that perhaps more spirits should progress by pilot level, like Trust and Refresh. Especially those giving static bonuses.
Trust and Refresh are special because healing effects are rare. However pilots are getting boosts to movement and hit/AC and damage from plenty of other sources, so the spirits that boost those don't need it if you ask me.