Good point. Well, the simconnect interface is the main FSX one, but one can trick e.g. ASE to run in the FS9 mode and then only using FSUIPC.

On the weather addon freeware, you can pick FSUIPC or SC, as you like. By this, it just comes with other downsides in regard to the SC interface. Unfortunately, there's no golden mode to be used, hence my hope for a completely new sim or just some major improvements over the FSX origins. Especially on the weather system, which is very awkward at times and limited on the detail.

We often fly like on rails in the sim, even at tricky locations.