Its tempting, but a less exciting proposition than an official RS stripped model for two reasons:
1.) Insurance is much more of a hassle for modified cars than it is for standard factory cars (unless you qualify for classic / specialist insurance like you would on a 964 RS replica for example). Stripping + caging is something I would certainly declare.
2.) I could strip and put a half cage in my R26, but that wouldn't add all the appeal and experience of a .R - wouldn't have the tweaked suspension, seats, harnesses, ti-exaust etc.