I don't know if you had thought about this, but it's a really sad effect of cost increase that there are almost no more privateers in Formula 1.
The engine limit from 2004 on will probably be a good something, as private teams should be able to buy engines for a smaller price, as they would simply need fewer engines.
On the other hand, an engine ruling would not solve the complete problem, certainly not of the teams that have their own engines or are backed by a great engine company. The money invested there will probably be the same, and more money will go to development...
In fact, as those teams don't pay for their engines, they would still need the same amount of money for research...
I personally think this is a problem that must be looked out for very carefully, and more so, I think the engine ruling must've been there in 2003. It would have been a nice start.