It's completely possible, but here the full context:
You can add stats and even recreations to mounts in all episodes and server files, but here comes the problem:
- Your ps_game must have a function for mounts with stats, otherwise the 'real' stats gived by the mount are never gonna have an effect.
This is only possible on shen ps_game, aka 'pure EP6' files and perhaps EP7-8. I have maded a server with functional mounts with stats and they worked partially*
- * Your game.exe also needs an edition to visually show the stats you get.
The extra stats never show on the (T)Interface and also on your character HP bar and final damage calculation.
For a example if you have a mount with 1000 STR and you do 500 damage with an attack, equip the mount and it's not gonna show more damage, even if the damage should be 3000-4000 or more, it still shows 500.
The same applies for final magic damage, critical and evasion and reduced damage incoming and HP.
This can led to visual issues in PVP, albeit minor, but undesirable.
Conclusion:
You can make mounts with stats and recreations in EP6 shen ps_game, but your players are not gonna notice the stats and perhaps you are gonna have minor visual bugs on the client final damage calculation.
Worth the effort? Perhaps if your mount give a few stats, but for high numbers it's not advised.