I don’t know how difficult it would be technically but the developers may be able to utilize the some of programming that already exists that determines your team bonus level for a particular Kingdom & or Type. This would scale based on the number of troops you fielded in that category.
You would then get bonuses for having 2/3/4 troops respectively. (Instead of all/nothing) So for example on console this week (keeping the same bonus) 2= +100, 3= +200 4= +400 Gold.
My original post about the creation of weekly bonus events to encourage a rotating meta.
As a aside: I am so happy they implemented this feature. The developers DO LISTEN to the community! This is just one example.