aren't rx7 rotary engines massively fragile to big boost but run very well with moderate boost off a big turbo (ie, lots of air)? Therefore I guess a big wastegate could be used to quickly modulate (ie, dump!) boost pressure from a big turbo that comes in with a bang all of a sudden to keep it within limits?

all of that said, the size of W/G the OP suggested does seem like overkill.