Has anybody messed with this yet?
https://www.linuxsampler.org/about.html
I see that it can load gigasampler format files as well as sfz files, both of which I have a fairly good selection of. I also see that it has a backend engine that is decoupled from any frontend, so you can use different interfaces for it. One is written in C++ and the other is written in Java.
It looks like a fairly involved process to get all setup, but I'm thinking that once you get a frontend and backend talking to each other, along with all the midi and audio connections mapped out that you might be able to save it all as a track template in REAPER, so using it later down the line would be an easier task.