Make every clan able to select a "Capital Fief"
This fief will have some kind of bonus which makes it much easier to defend.
I.ex double or even triple amount of tickets and money for defensive battles.
Double is not really that much anyway, since larger clans will have many more fiefs, and a much stronger economy.
It is of course possible to exploit such a feature by creating many strategus factions within one clan, but I do think the big clans have some kind of "Code of honour" preventing such abuse. In any case it would be only for defensive purposes and not possible to abuse for offense. To prevent abuse by big clans, one could i.ex implement a "transfer tax" of 20% unit/money loss when trading troops between factions.
Hopefully such a change would make the map look much more complex with many more factions, and hence more activity, and also add a new layer of strategic depth. An alliance of small factions could have a chance to at least defend against a big-clan assault.
What do you think?