The currently accepted "proper build" HP level is about 130 plus at the wheels, or about 150+ at the flywheel.
RX-7 power is funny...if you talk to Mike Van Steenberg at ISC in FL, he says 115 at the wheels is more realistic, but others (Yaw, Susko) say they see more. The cars in the SE run veeeery strong...suggesting that they must be putting down more than 115.
So, at 133 say, the Rx-7 would need to gain some weight to run in B. Around 100+ lbs.
There is the issue of the change to narrower rims, but that is considered (rightly or wrongly) to be somewhat minimal.
And while actual lap times must be taken with a HUGE grain of salt, looking at some large amounts of significant data suggest that as is, the RX-7 would be a tad strong for ITB. Nobody, even members of the ITAC who own RX-7s want the car to be an overdog.
The cage situation HAS seen exceptions, and DOES have some irregulaties and inconsitancies, however, there is an awareness of that among the rulesmakers, and a desire to clean things up in that regard. So, at this point, exceptions are pretty much a non issue.
The cars only real option in a movement to ITB classing, is a restriction of power. The approximate flywheel number would have to be limited at 140 max, wheel hp to 114 or so, if it were to stay at it's current weight and avoid recaging. It is thought that most ITA cars built with .095 cages would balk at recaging.
Rotaries are tricky to class though, as the torque numbers are dismal. My cars last engine showed about 130hp at a bit over 7K rpm at the wheels and 103 pound feet of tq on a Clayton dyno. (Known to yield strong numbers compared to a Dynojet, for example).
So, a move to ITB would require a properly sized SIR, and a change to 6" wide rims, if it were to stay at it's current weight.
Or maybe a little sugar in the Nissan and Honda tanks in ITA might do the trick there,