Well, I don't own Notum Wars yet so I'm not exactly sure what all is involved as far as attacking/defending/owning towers, but heres an idea from outta the blue. Implement a way to contract the defense of a tower to another guild. In exchange, a regular salary could be paid to the defending guild with bonuses/commissions paid for sucessfully repelling attacks. Of course almost any variation on the method of compensation would work as well. In addition to the salary, all, or a fraction of, the buffs and bonuses afforded by tower ownership would be bestowed on the "officially" contracted defending guild. However, with every up there is a down, therefore there must be some penalty in store for the defending guild if it defaults on a contract somehow (intentionally losing the tower) or if it ends up losing the said tower/land to an aggressor. The ingame penalty should be somehow scaled to the magnitude of the defeat though, and as such preventing smaller, less powerful guilds from taking on contracts too outta their league.
As I said, I don't own NW soooo, I might be outta touch with all the changes, but...I kinda wanna see the rise of mercenary guilds, might make things a bit more interesting
My two cents,
Cheers