Unlike MSF which could get away with this - as it uses the same pieces to make "custom" parts for each hero. All the crafted pieces in SWGOH are shared among all toons. They can't like... change the gear to apply negatives.
The only fix that's going to make any sense and not derail the NS train... the only one that's not going to destroy the investment of multiple zetas and gear among a number of toons... is they take her unique and inverse the health/protection/defense gained by each gear tier. So that by G12 she's essentially weaker - but then also faster and hits harder (a bonus) then she was at g4.
This makes her a better paper zombie - requires gear - then encourages it with the speed/dmg gain from gear levels. No need to reverse mods - people simply need to be cognizant of how to best mod the zombie - as with all toons.
I don't see anything else that doesn't destroy the concept.