There’s an accepted GHC proposal to switch to -threaded by default: Compile with threaded RTS by default by ulysses4ever · Pull Request #240 · ghc-proposals/ghc-proposals · GitHub
When trying to implement it I wasn’t able to figure out a good way to deal with GHC’s test suite. The MR is still around but it’s probably worth nothing at this point because of how old it is: starting from scratch may be easier.
I encourage to try implement it if you have energy, and would be happy to participate. But you’d need guidance of someone from the GHC team who understands the inner workings of the test suite (probably @bgamari).