When I started the limit was not having much money. The rules were fairly open, and we didn't lack ideas but we did lack resource to evaluate all the ideas and to put the promising ones into practice.
The first big change was fag packet sponsorship which gave Lotus a huge benefit (probably >10x more money). Little by little everybody got fags. Then the big car companies raised the ante again (about 4x more money).
Nowadays there is enough money to do mindless 1000 monkey type developments if wanted.
I don't think it could be properly controlled, but if it could a budget rule would even things up, but a huge number of existing people who are mainly there for the money would go, which would maybe not be a bad thing. Do you spend money on the driver or the wind tunnel etc..