Copy Saver is boring, pretty much always useful, and makes Translator look like trash. At least SEPI has some conditionals on your free loot.
Fusion Saver is unexciting because Fusion is limited more by 'running out of viable things to fuse' than it is by currency.
Revive Saver is boring, awful, and pretty much made redundant by quick dismiss (spend a free action to prevent your demon from dying, or be able to revive your dead demon for 75% the cost? Hmmmm....)
Translator has a similar problem to Fusion Saver- the real limiting factor is ability slots and ability access, not credits. Getting to 8 summoner skills is not particularly hard, probably requiring maybe 6000 credits in an average game. Getting to 8 GOOD skills requires finding the right demons, and successfully linking with them. I'd never actually get it myself at level 5, even if Copy Saver didn't exist.
SO THESE ARE MY RADICAL NOTIONS
Copy Saver-> Honestly, just delete this and keep SEPI for the 'I want monies' upgrade.
Revive Saver-> Possession- Lets you replace the ENTIRE skillset of a living demon with the skillset of a dead demon. This deletes the dead demon from your coffin. Alternately, call it Seance and let dead demons teach their skills to living demons, possibly for higher prices.
Fusion Saver- TRIANGLE FUSION
So you take THREE demons and cram them all together into an invulnerable monster that actually isn't that great because of the HP penalties from having too many resistances. Hmm. Well, maybe I don't have any radical notions for Fusion saver after all.
Translator- The summoner can learn skills... FOR FREE(But only on 100% cleared levels, to prevent tactically tedious skill swapping). See above for why I don't think this would actually be unbalanced.
Also this lets inquisitive players test out strategies and abilities for themselves without worrying about ruining their credit rating.