[it depends]

I think the crystalline armour being mod'd into the impeller driven sidewalls would make sense. The degradation would be slow at first, then rally oick up as on or more impellers went down. I don;t have the books handy, but I am pretty sure that the sidewalls went down altogether, not in sections? So if one impeller blew, that whole sidewall would be weakened all over, not just in the specific area that the hit landed.

Rolling to present the top or bottom wedge was more effective for Groups of ships. Rolling on your side might block a few of the beams from a BPL, but some would still curve round and get to impact the sidewalls. I think I could manage to not have that ability, although.... if you took one of the sheild rechargers, and turned it into a time limited invulnerablity, that disabled your weapons while activated? Might be a large sized headache though, especialy if you wanted to try to animate it.