You've described the build I'm currently trying to imagine myself! Be interested to see if there were any frames similar to the UP but less bankrupting. I know the Bish Bash Bosh! looks to be vaguely similar but probably not versatile enough for what you're looking for.
Edit: slow afternoon has lead me to this, which looks close to the UP, lots of mounts
You've described the build I'm currently trying to imagine myself! Be interested to see if there were any frames similar to the UP but less bankrupting. I know the Bish Bash Bosh! looks to be vaguely similar but probably not versatile enough for what you're looking for.
Edit: slow afternoon has lead me to this, which looks close to the UP, lots of mounts