methods for establishing dues

I live in a partially (45%) completed townhome development in Idaho which has just been purchased by a new developer. We formed a "Friends of Pepperwood" group to help us deal with being abandoned by the previous developer and the new developer is being very friendly to the group. He has actually given us the opportunity to propose changes in the CC&R's, so we are working on that.
I am looking for a formula that would be a compromise between the A)having all the homes pay the same dues and B)a percentage method where dues are based on the square footage of the home.
The homes range in square footage from @1200 to about @2400. They are sitting on lots which vary from .07 to .1 acres - often with the larger homes on the smaller lots due to the archetectural design of the development.
I can see many issues here, but it does seem unfair for alll the homes to pay the same dues when the larger ones are worth twice as much.
Ideas???

Beth, our COA bases assessments on SQ FT (eight different floor plans) and both the declaration and state law require 100% yes vote to change. It’s nice that the new developer is willing to work with you but you should have an attorney versed in real estate helping you with this. Just one of the hurdles I can see is the fact that of the 45 % sold I imagine most are mortgaged. If the mortgage states how the assessments are to be done or the percentage of the common areas and this changes it then all of the mortgage holders will most likely have to sign off on it. Not to mention convincing the owners with the bigger homes that they should pay more.