A powerful editor would easily be a substitute for instrument definitions. After all you are wanting to select patches and maybe edit them in some way and an editor can do that in spades. I have several and I am doing that now. Even though editors are using SYSEX to communicate with the synths they
can be used in tandem with Studio One. You can define the same midi ports from Studio One and an editor to the one synth. They will both happily talk to it.
I agree though that Quest currently is not an ideal solution for a few reasons. One is that it is very expensive and what if you only need a few editors instead of the ten thousand they give you for the full price. And also as some have said here they are not fully up to date with the latest hardware synths either. Although probably being addressed in the new version to come.
They need a different business model because I have say 4 editors or so now and might only need another 3. There needs to be a cheaper way to able to just buy a few of them.
To those who think hardware synths have gone away they are wrong. 2017 was a bumper year for hardware synth releases.
And also to those who are concerned about the non musical uses for midi then it is a moot point. After all it was invented for musical reasons first. Granted it has been used for other applications and that is great but not a good a good reason to knock a DAW just because to cannot handle another use that only very very very few are needing. Then you get the DAW that can do it. Simple as that.
If Presonus are developing further midi development in Studio One it will be for musical reasons first. That is for sure and rightly so.