In my particular set up I try to keep as much add-on scenery as possible outside the simulator (I believe this is the is the considered wisdom) however I also like to keep everything related to P3d on its hard drive, and similarly everything for MSFS on its own drive.
Which is EXACTLY what our installer allows!!
The "wisdom" you are referring to, was STARTED BY US, in 2017, the day P3D V4 came out, when we updated our installers to "install sceneries outside the sim", by using the add-on.xml method, instead of placing everything inside the sim that was the norm before that. Back then, I do recall some users attaching us to be the usual "innovative weirdos", using a "confusing" method (everything new is always confusing) of the add-on.xml, instead of the "easy" (messy) old way to place everything inside the simulator.
Of course, LM was right to have introduced this system and to suggest using it as the proper method to install a scenery, and of course we were right to be the first adopting it because, in time, users started to see the benefits, other developers followed us, and THEN this became the "considered wisdom".
Sadly it doesn't seem that your ecosystem will allow for this and I will have to choose one drive or the other to install everything (or the C: drive). Not the end of the world, just a pity.
Our system SURELY lets you install "as much add-on scenery as possible outside the simulator", and this is valid for both simulators. While in P3D this is supposed the official method ( even if not all developers follows it, but we do, before anybody else did ), with MSFS we reached this worthy goal we surely believe it, by using Symbolic Links to the Community folder, precisely to allow keeping things "outside the simulator", even in a simulator that wasn't precisely designed to do that.
But what the requirement of keeping the FSDT products together, would reduce in any way your desire to "keep add-ons outside the simulator" ? They are two completely different things: we SURELY keep everything outside the simulator, we just keep OUR stuff together, and that's it.
An eventual method that would use two duplicate FSDT installation, one for MSFS and another one for P3D, wouldn't improve at all on your goal of "keeping things outside the simulator", because that's already done, but it would be WAY worse and way messier because:
- We would create lots of duplicate files, wasting space your drive for no reason and no benefit. This because many of our products SHARE files, which would be otherwise duplicated if we had two separate FSDT installations.
- We would have a messier and more unreliable update process, because two (cloned) updaters would have to check and update files in two different locations that would have been otherwise identical otherwise. Even if the updater might be one, it would still have to deal with a doubled install location, that is more complexity with zero benefit, but surely more disk space taken on *your* disk.
- You would have to deal with adding multiple antivirus exclusions for the install folder, instead of one.
So no, it makes sense for many reasons to keep OUR products together, and we should now it better, considering we made the software, the products, the installer, the updater, and we know how they work, and we know you won't gain *anything* by splitting the installation in two, when the files are ALL already installed outside the sim.