Not SaaS, but I had an idea for using a CPU emulator to run a compiled binary under Java, with libc implemented in Java so standard file IO works. I punted on the idea because it seemed pretty difficult and maybe take six months. I recently gave Claude a Java RISC V emulator and a partial bridge between Java and libc, and in under an hour, it could run bash and sqlite from Debian.

I have no idea how correct the code is or what I'd do with this, and I have no plans to publish it for those reasons.