Conflux – 9th town for Heroes 5.

however, it doesn't feel like a home for the Spirit faction; I believe that T1-T3 create the base for the faction, and there's a spirit-blacksmith and 2 robots.

The Academy from levels 5 and 7 is, in any case, a mixture of all the houses – Anima, Material, and Chimera – and this is a compromise solution. Otherwise, it would be necessary to create two more factions for each house.
And thanks to the variability of T7, even though it's a controversial decision, it can be said that the player has a chance to influence the development of their city towards the Spirit or Construct house.
I still dream of a mod based on NCF, where they create three sub-factions for each of the Academy's houses. But even here, the question is: if something can be devised for the Anima and Chimera houses, it's unclear what to do with the Material house...