You don't need to supervets the 2 repairman to hit the cap.

All depends on the choice of the engineers, if your engineers are ellite ( they suck balls) then it is probable that one need to supervet. Else, roll a base 11 repairs with good engineer  ability.

Restorer is useless in a BB. If anyone wants to level a restorer and get frustrated at the end, because he or she realize finally, be my guest.  Because I experienced this, and if you wish to have advice, better not have restorer.

You can also get to hit the repair cap faster, by rolling good repair stat on your gunner/scout/BO.

I have a level 119 BVE Restorer on my Nebraska crew, and I have an EBVE Restorer for my L1 crew because it seems to allow me to soak up more damage than normal even after hitting the SD cap. I've done my tests and made my conclusions in the past, and I'd say use one if you want to.