In this proposal is the goal a) to save money or b) to penalize or handicap new technology?
If the goal is to save money this approach could easily backfire and likely will. If there is no control upon the number of tires a FF racer can purchase during the season and it is permissible to run new "hard" tires at each race you have solved nothing. Actually, I think it will be worse as a new hard tire will work much better than a seasoned hard tire. Reference comments by Dave W and John Robinson. (FYI I won this year's Sprints on 2005 Runoff's qualifying tires.) The proposal has no substance although it certainly has a tremendous amount of curb appeal.
If the goal is to handicap the new technology this seems to be a strange way to accomplish it. I think this is absolutely the wrong thing to do and believe those who think along this line belong in a spec series or vintage racing. I however would propose that if this is truly what you want to do then simply invert the grid, handicap "new cars" by a certain amount of time per lap or throw everyone in and run by ET brackets. (I would certainly favor giving a certain amount of time for each year a car is old!)
I am not aware of any FF program that mandates the compound if they are not under a "spec tire" program. I am not sure what you are referring to by the term "control tire".
Finally, if FF racers want to run a hard tire, a radial street tire or a tractor tire they are free to do so TODAY. Why aren't they? Because they think they will not be competitive.
Once the tire rule is adopted and the gap is not bridged (and it won't be) what then? Well then we will have to look at limiting other items. shocks, head porting, light wheels, new cars, better brakes, testing, races entered....the list is never ending until we do get to a spec car/series. You are attempting to legislate competitveness and it doesn't work.
As noted, there is no reasonable method to limit spending. If the money is not spent on one thing it will be on another. It is a simple fact of life that there is always going to be someone with more than you. If you equate spending to performance then there is no way to level the field.
The key to success is to maximize your perfomance for your budget and to play in a game that you can afford to spend what is necessary to run where you want to run. I would suggest that the one bright spot of FF is that it rewards those who work hard and think. Certainly an adequate budget helps, but hard work and innovative thinking can and will win races.