I wrote an RV64IMA emulator recently. I just needed a virtual CPU core that could boot linux, and RV64IMA seemed like the simplest way to do that - and I think that's more or less true.

But then I wanted to be compatible with off-the-shelf toolchains and binaries, and I found myself needing to extend the ISA profile to RV64GC. Not a huge lift, but it involved pulling in a softfloat library. That got me as far as booting Alpine linux.

And then I wanted to be able to boot Ubuntu, which needed RVA23, which was comparatively a much bigger lift, involving the vector instruction set among many other things. At this point I think I'd have been better off just emulating aarch64.