Object rearrangement.

It’s not exactly a new feature. I think almost everyone remembers how, in the campaign for the undead, Markel turned mage cities into Necropolises. But then there was a clear explanation for this (a special dark ritual that kills the inhabitants and turns the city into a large graveyard), it cost a very decent amount of money, and the resulting Necropolis was level 1. +This was only possible with a special script.
Here, no script is needed, and there are very few restrictions on the conversion. The obvious drawbacks of this are:
- unambiguity of tactics: there is not even a choice of whether or not to convert. Why ask us then? They could do it automatically, and that would be almost the same, and they could not charge any money at all.
- the absence of the need to carry units of other factions with you: because this is only possible if there is no conversion, but why not do it? So that you have to run to the main city every time to replenish your forces, giving the enemy an additional advantage? This point is especially sad when I remember other games in the series: in H3, I constantly carried a mixed bag of units from different cities, which added a lot of interesting tactics and made each game different from the previous one. In H5, due to additional restrictions on the building development, this became less profitable, but nevertheless, adding some casters from other castles was often useful. In H6, there is no benefit, only harm.
- A logical drawback: how does the transformation happen, for example, of an orc city into a naga city? The nagas come, wipe out the orc population, destroy their buildings, and then reproduce and build their own buildings. All this in one day? In terms of city building, the games in the Heroes series have never been very realistic, but this is too much.
In my opinion, it would be more logical to give the opportunity to convert only one faction for a very large amount of money: Necropolis, make this their racial feature, since it is easiest for them to explain. At the same time, there would be no "teleportation" of units from one city to another, and for balance, this faction would be weakened as much as possible at the start and made the weakest when playing from one city: with the intention that it could potentially catch up and overtake everyone if it captures several enemy and neutral cities.
I forgot about the advantages. I see only one advantage: if there are many neutral cities on the map, then the randomness in terms of getting better or worse ones is eliminated: in any case, we convert everything. But personally, this advantage does not matter to me.
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It seems to me that if everything is justified with forts and dwellings, then with cities it is too unbalanced. It seems to me that for the balance of multiplayer, it would be better if all buildings in the city were demolished. In this case, the cost of rebuilding could be reduced: 1000 gold for a regular building and 2000 for a unique one. In this case, a fully built city with two unique buildings and a Tears of Ashi building would be demolished for 29,000 gold. What do you think?

From the point of view of balance, everything is normal, everyone is in equal conditions.