As the ghcup team wasn’t invited to that meeting, I can reply here:
What you’re describing pretty much sounds like a re-invention of ghcup, which already exposes a (probably brittle and imperfect) API: https://hackage.haskell.org/package/ghcup-0.1.14.1/docs/GHCup.html
Adding more exectuables to ghcup is rather easy. As was done with HLS recently.