From the outside perspective it may sound easy, but I assure you it is not.
This problem does not apply to just the faf mod. It needs to be applied for fafdevelop and fafbeta as well, and for these you surely do not want to get a banner, but it still needs to be covered. Still then we didn't talk about the on-top featured mods like coop or phantom. These may or may not need to be updated depending on the game you want to play.
For the FAF client it's hardly possible to detect the currently applied version, since any given file could belong to multiple patch levels and things get messy with on-top featured mods.
The lobby server doesn't track the played base version and on-top featured mod version. It doesn't even know that versions exist at all.
The patch generation happens outside the lobby server and it would need to be notified about this change. But some deployments of featured mods happen partially manually, so there is not even a way to do that right now.
TL;DR: It is possible, but would require fundamental changes to patch handling in FAF. And all that for the few days a year were we release a patch. So it's not likely it will be tackled.