I actually think we could get the Tzimisce as a playable clan in a video game BUT Vicissitude is gonna get nerfed hard and the options for the discipline will be very limited compared to what you can do in the tabletop.

Like the first to third dot of Vicissitude would probably only allow you to move and add dots in your physicals and appearance. Give yourself bone claws, armor and maybe have a few options to change the appearance of your character. Horrid form would be the easiest power to adapt into a video game, since all it does is turn you into a big monster that makes you stronger, tougher, and faster and bloodform can be used as traversal power.

I have no idea what they would do when it comes to Szlachta but if you could create them they would probably have a default model that you cant change. Even with this water down version of Vicissitude, it would be very difficult to implement into a video but I don't think its impossible, unlikely yeah, but I think if devs really wanted to add the Tzimisce they could.

But I agree that clans like the Lasombra, Ministry, or even the Hecata would be easier to adapt into a video game then the Tzimisce.