RTF is a global modification that replaces all towns in the game.

I think that the Orc city could suit some Barbarian race, for example, you could make desert lizards with bronze scales and sand wyverns instead of the current ones.

That's possible, but has the issue with the city screen been resolved?

Added 1 hour 12 minutes ago
Or you could abandon Wintrial, replace it with lizards, and replace the Orcs with... desert Orcs. The demons in Ashan always act as the main antagonists, and I think it would be more interesting if there were some other Factions.

Added 43 minutes ago
If the idea with the Orcs doesn't work out, and the lizards do live in the deserts, you could give them Haitherrants instead of Coatls.


Added 31 minutes ago
I came up with the Orc composition, I'll write it down so I don't forget it later :)
1. Goblin - melee
2. Gnoll - ranged (give small lizards to the swamp creatures)
3. Wolf - melee
4. Shaman - melee, spellcaster
5. Ogre - melee, tank
6. Troll - ranged
7. Cyclops - melee (and give the MH to the Wendigo from Wintrial)
True, with this setup, the Orcs won't have any flying units. But this could be a feature of the Faction.