I've been playing around with my broken up version of the castle fort upgrades that make up the difference between a tribe and a castle. I just finished upgraded one to a castle for the first time in my run. I do like this a lot, it gives me stuff to spend my money on that I can actually afford with some regularity. Especially once I saw how expensive most of the new castle buildings are. However, I can already guess that there's going to be a problem in that it would be quite tedious to upgrade a tribe to a castle that you can easily afford. This set has eleven buildings and it's already tedious just going through four when you have absolutely no problems affording the upgrades.
Honestly, I think the option to just straight up build a castle or city without needing to go through the tribe stage really should be included. After a certain point, players aren't going to want to spend all the time it takes to go through all the necessary upgrades for each new castle or city. A castle or city can mostly take care of itself so you can just build them and turn them over to a new vassal, a tribe isn't just fine on its own. Especially since you can't build another holding in the province until the tribe has been upgraded, you need to fully upgrade that one first.
Alternatively, a special 'skip' building could maybe be added to the tribe? It seems a bit pointless though, better to just skip straight to the holding building once you can afford to do it regularly. Upgrading tribes individually would still be preferable while your income is still below a certain point. But once you're making like 20+ gold a month, you'd never want to take the time to upgrade a tribe's buildings one-by-one and babysit it to make sure the next one is being built once one finishes.
Honestly, I think the option to just straight up build a castle or city without needing to go through the tribe stage really should be included. After a certain point, players aren't going to want to spend all the time it takes to go through all the necessary upgrades for each new castle or city. A castle or city can mostly take care of itself so you can just build them and turn them over to a new vassal, a tribe isn't just fine on its own. Especially since you can't build another holding in the province until the tribe has been upgraded, you need to fully upgrade that one first.
Alternatively, a special 'skip' building could maybe be added to the tribe? It seems a bit pointless though, better to just skip straight to the holding building once you can afford to do it regularly. Upgrading tribes individually would still be preferable while your income is still below a certain point. But once you're making like 20+ gold a month, you'd never want to take the time to upgrade a tribe's buildings one-by-one and babysit it to make sure the next one is being built once one finishes.