I personally never have used reaper, might do if there is no support for other DAWs later in the future.
some new DAWs I would love to see in FMOD is, Studio One, FL Studio, maybe WaveLab?.
Studio one feels a bit more appropriate for FMOD since all the new features introduced in 6.6, with spatial audio, surround etc.
Technically, every DAW is compatible with FMOD Studio even without a specialised integration, because you can simply set the DAW’s output/bounce out/build/bake folder to your FMOD Studio project’s assets directory, and set the DAW as your external sample editor in FMOD Studio’s preferences window. The Reaper integration adds some convenience features to streamline the process, but doesn’t ultimately do more than you could achieve with Reaper and FMOD Studio already.
That being said, if there is a specific DAW you’re interested in, and it has an API or public-facing hooks that can be used by integrations, let us know!