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No, in principle, there are no problems with placing a unit at level 7. The other issue is that by removing the angel, you have to overhaul the styling and unit list of an entire Castle, change the lore, and work around general fantasy stereotypes.
Right now we have a "European" castle. This gap can be filled by changing the "national" orientation. You could make a castle in the style of Ancient Rus. That is, the same units would come first, but dressed in appropriate armor. And for level 7, you could place a prototype of Perun: a Thunderer with a hammer.
Naturally, everything can be left as it is. However, if angels are removed, then monks—the bearers of faith and holders of the power of Light—and griffins, which look so organic next to angels, also become illogical. And in general, I consider separating the guardian angels to be wrong.
Right now we have a "European" castle. This gap can be filled by changing the "national" orientation. You could make a castle in the style of Ancient Rus. That is, the same units would come first, but dressed in appropriate armor. And for level 7, you could place a prototype of Perun: a Thunderer with a hammer.
Naturally, everything can be left as it is. However, if angels are removed, then monks—the bearers of faith and holders of the power of Light—and griffins, which look so organic next to angels, also become illogical. And in general, I consider separating the guardian angels to be wrong.