Just look at the number of threads where we are discussing backward compatibility, and explaining why the opposite ("forward compatibility") cannot work.
And next, look at existing cases where we expect a certain updated file format/version (e.g. jsbsim) and show the corresponding messages.
The other option would be introducing a separate dialog with its own "logwidget" that collects aircraft related debug messages (info, warnings, errors), and maybe categorized using tabs, so that aircraft developers, and end-users, can more easily review if something is supported or not.
Note that it would also be possible to allow aircraft developers to encode/use conventional SGConditions, i.e. conditions in the form of property checks (analogous to effects), including even embedded bindings (fgcommands/Nasal), which would require 30 lines of Nasal code that already exists elsewhere - at which point it would be possible for an aircraft developer to decide
if fgversion <= 2.00 fgcommand("exit") - maybe in combination with an actual dialog explaining what he is trying to do (aka: playing a MP3 file on a Walkman)
I don't think there are too many people trying to use USB flash disks on 8086 PCs these days, but that is basically what end-users are doing once they are trying to use the f15/shuttle in fg 1.0x