You make a solid point, especially about recruiting against people with so many scholarships open. I always tend to balance my classes by copious use of redshirts and the occasional JUCO. But I can initially think of two consequences of that which I would see as negatives:
1. Sims can still build superclasses, and it would take even longer to rebuild a Sim that had done so. I have five teams, and I've signed up for them all in the last six months, so they're fairly fresh in my mind. Three of them were taken over directly from Sims, and I have had first classes of 5, 6, and 6. In each of the latter two cases, I took JUCOs to balance things out a little bit, but I wouldn't have been able to do that without $18,000. With this rule, I could see people stop taking over teams that don't already have perfectly balanced classes. And to be honest, it's already hard enough to find teams that don't have classes of more than six. I'm looking at moving to D2 in one world, and in one of the (relatively strong) conferences I'm looking at, I basically have a choice between a team with seven seniors and a team with ten sophomores.
2. Suppose you've built a team with relatively balanced classes and are currently recruiting. You have three open scholarships, four seniors, three juniors, and two sophomores. You sign two guys relatively easily but are in a battle for the third. Right now, it can be good strategy to take a gamble on a battle you're not sure to win. It might put you behind the eight-ball a little bit the following year, losing some class balance and needing to find players who can start as sophomores, but it's a risk worth taking. Under your proposal, it's not worth battling unless you know you can win, because if you lose, you're stuck with on $12,000 and you need to find five players, including at least one who is good enough to start as a sophomore. I see that as a negative change.
Just my $.02. Good topic.