This is a pretty awesome mod. I saw what you said about fliers and what you plan to add. I run a server that really likes not having flying mounts. I plan to add this to our server and keep the fliers in. We have a custom engram list so keeping them from being able to fly will be easy, with the exception of the wyvern and griffin as they don't require saddles. So these two I'll have to disable though it'd be fun to have them.

I don't know how much more work it would be but if you could make saddles for the dinos you add in that don't require them, and have them have a saddle requirement to be able to ride them. Then aberrant servers could easily have them on their servers for the additional creatures to interact with and see, but server owners could control what's ride able by simply disabling the learn engram for the saddles.