[@Kho] When you account for Holy Sites, you can still very easily level every turn using current Might mechanics and a 2 x Lvl creation value. This table assumes that Might spent on Holy Sites don't count for levelling purposes.

Level at start of turn - Carryover Might + Might generated - expenditure, level/don't level, Might at end of turn

1 - 0+4 - spend 2, level, end 2
2 - 2+5 - spend 4, level, end 3
3 - 3+6 - spend 6, level, end 3
4 - 3+7 - spend 8 on a Holy Site, end 2
4 - 2+11 - spend 8, level, end 5
5 - 5+11 - spend 10, level, end 6
6 - 6+12 - spend 12, level, end 6
7 - 6+13 - spend 14, level, end 5

Of course, even if there's a 2 Might cap on creation value, you'd have to be extremely active to level at this rate, but maybe it would still be best to compromise and have a cost set on every level.