My
guess would be you could do all you mentioned except for ditching the standard three point belt. Multi-point racing harness are technically not legal to run on the street in most states (because most fire rescue are not trained how to release them). I would also guess street legal would include still having all lights, signal indicators and reflectors. It's your insurance company that will gladly charge you more for not having any of the airbags in place.
If you want to DD a gutted, caged car more power to ya! LOL!