maybe instead of only having houses there could also be clans of, like people who dont really want to be in a house but would like to participate in wars?
i think it would be fun and a lot of people would do it

This was brought up a long time ago, and it was thought about.... for less than 5 seconds.

Clans would be too much trouble, and like you said, a lot of people would do it, which in turn reduces the amount of people joining a house, which is one of the major things in FE Wars.