but are better than current shield extenders

Shield Extenders naturally regenerate. Ferroscales are harder to fit, and don't regen. Even though its just an opinion, I think shield extenders are better.

i meant reactives srry

I believe both armor and armor repair skills should apply to reactive plates (currently i don't think any skills or bonus apply). I also vote for an increase in the health and repair rate. The basic plate is nigh worthless and the only one i see decent is the complex but just marginally for what it does.
I think the rep rate should be tiered as well. I understand you don't want them to be as effective as an armor plate and armor repairer together. However the fitting cost especially in PG and CPU are pretty high and the stats should be a bit higher than they are right now.
increase hp rep by 1 per tier so a reactive plates give 1hp 2hp and 3hp rep basic, enhanced ,complex respectively.
I also think a slight boost in hp would give more incentive. i say a basic should give 30hp at minimum i am actually using reactives on my min suit to give me the armor buffer while i use the reserve slot for regulators. So far its a hit and miss although complex plates aren't too bad but i at times i feel they do little considering fitting cost.