I said I would add another rare resource as a bonus for upgrading later.
How often and at what stage of the game can you steal another player's dwelling on regular maps? Often, it's not even captured; it's just not worth the distraction.
If we're talking about a neutral, non-native dwelling, then yes, it's only for the Roach faction. But this problem can be solved in another way by doubling or tripling the growth from all external dwellings; then, even neutral dwellings won't be ignored. This approach allows you to combine troops instead of accumulating a homogeneous mass.
If we're talking about the very late game, then ignoring such dwellings is logical because a well-equipped hero ignores weak artifacts lying around in slots that are already occupied. The same applies here.
In any case, even with conversion, you're essentially buying a new native dwelling, and it should cost accordingly (at the appropriate level), not 500 gold. I don't understand the double standards: developing mines is expensive, but developing dwellings is free.