For
Imbuements, its' easy:
"Sword Power" [10]- Imbuement Talent 5 (Accessibility (Fatigue Cost Reduction Only), -80%) [10]
Features / Notes: Doesn't count against maximum talent levels (if any). Removes the fatigue cost for any use of an Imbuement Skill that isn't a critical failure; critical failures continue to cost the character 2 FP as per normal.
... works for the standard magic system as well. Same point cost even, just replace "Imbuement Talent" with "Magery" and change the features/notes as appropriate; make it leveled (at [10] per level) and it'll reduce the energy cost by 1 per level for your bigger spells.
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But, no, the way you've built that Regeneration isn't RAW-compatible and isn't going to play nicely with what I understand of your intent.