What if they were to add it so that you needed to drop at the town (10) AND field (10). 20 troops total for a base and/or made it to where it would require 10 for V-base, small field; 20 for Port and Med field, 30 for Large field? Would likely increase the size of the horde though.
These are just questions, not a wish for implementation.
As mentioned earlier, it would be neat if the town sizes varied based off the field size.