Ah, the remark about the planes in FS9 (FS2004) format is very valid.
In P3D v2, the FS9 planes are showing correctly, but unfortunately their virtual cockpits are not clickable at all anymore.
In P3D v3, the virtual cockpits of the FS9 planes are clickable again !
But only for the switches/levers that are modelled in 3D. The 2D stuff will still not be clickable at all.
This limits drastically the amount of FS9 planes that can be used in P3D v3, unfortunately.
However, the most recent FS9 planes have some 3D switches, so they can be used without problems.
For example, in the screenshots below, you can see the C-202 Folgore, an Italian WWII plane made by Manuele Villa. I have also successfully tested the Mig-21 F13 by Ivan Jurcarga, which is a very nice freeware rendition of the early Mig-21 variant.