The idea is like this:
At level 20 Main Building, you can merge/combine the buildings to become a new buildings and keep their functions as it is. The condition is the previous buildings must reach max level before merging.
The Mergable buildings are: -
1) Academy lvl 20 x Smithy lvl 20: The Research Center lvl 20.
2) Grain Mill lvl 5 x Bakery lvl 5: The Food Factory lvl 5.
3) Sawmill x Iron Foundry x Brickyard (lvl 5): The Hardware Factory lvl 5.
4) Marketplace x Trade Office (lvl 20): The Trading Center lvl 20
-When you opt to merge i.e academy lvl 20 buildings, this buildings will be get upgraded while the smithy lvl 20 will get destroyed and vice versa. Therefore you can plan what structure to keep and which one to destroy.
-All functions of the marketplace, smithy and academy can be access at the new upgraded buildings. The Researched and upgraded troops will not change and You can still upgrade or research troops after the upgrade.
-The CP production and population of its buildings will not change and it will be added to the new buildings.
-You will get extra space to build other things. 5 extra slot.
-The upgraded center/factory will have the corresponding level of the previous buildings.
-Maybe you can upgrade the factories lvl 5 to max lvl 10 or 20, thus increase the production bonuses even more.
- Not all buildings can merge.
- I expect the cost will be very expensive maybe around 40k each resources for research/trading centers and 20k for food/hardware factories.
- Will got confused at first, but later you will get used to it.
- Maybe you can only do this at capital.
- Expect some glitch and bug...
- What happen if the upgraded buildings got cata down to 0? Well, it can't be helped. you just lost 2 buildings in one go. You need to do it again from scratch. If it's not cata down to zero, then maybe you can re-upgrade its level with the same price of the combination of all the merged buildings' level cost.
- What will happen if you change the capital? Well, the buildings will be reverted to the previous buildings (before you merge) and you need to build the lost buildings again. From scratch.
That's all for now.