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

That's a shame. And how soon can we expect to see the Sanctuary or Temple in a similar... almost finished state, like the Dark Gnomes and Elementals are currently?

Let's take a look at what needs to be done:
Sanctuary:
1. Add effects to various animations (to hide their flaws)
2. Sea Elves
3. Giant Turtles
4. Balance.
5. Redo the second upgrade (on the Ice Nags).
Haven:
1. The existing creatures need to be "recolored":
downgrade - brown
upgrade - blue/brown
alt-upgrade - yellow
2. Arbalesters
3. Vestal (from Heroes 6)
4. In principle, you can also use the Shining Ones from Heroes 6, but it's not necessary.
5. Unicorn Riders
6. City walls from Heroes 6
7. Hero
8. Balance

Something like that.