[Clutch Dog]

Coming from the rotary world, there is a reason FC guys stick to 13B's. anyone who messes with the Renesis motor just uses the housing on the 13B endplates for the exhaust ports. there's a bigger aftermarket for the 13B and more a proven design, not to mention the cost per part between a 13B and Ren.

So yes it would be possible to swap a rotary into a s13. a) if you wanted to do that why not get an FC since they have the chassis that was build for that motor and will probably handle better because of it.
b) if you want to do something different why not source out something that would be a logical upgrade. even a vg30 would be something better then a 13B as far as torque and power output c) who gave you internet access.

The big issue with the Ren motor is that like the VQ is uses a CAN system that unless you completely redo the wiring harness for your megasquirt you'll be chasing weird wires and signals till it runs right, even then rotaries use a specially designed ecu and fuel map system it'll be hard for you to get that all in without hurting your motor. assuming you already have the engine and trans then good luck to you.