the sistem would be this way:

* First place guild can made an alliance only with a Low Level guild.
* Or the First place guild can only defend alone the cities.
* The amount of guild aliiance may be determined by the position in the ranking in which they are, growing by one as far they are from the first place. Ex: Second place guild can made alliance only with 1 guild, third place with 2 guild excluding the first and second place, and so..
* Or the handicap can be apllied only to First and Second place, so the third, fourth and so have no restriction number for alliances.