One way you could keep costs of the engines down would be to make the motors "claimers" You'd have to make an adequate comparison sheet to offset year of manufacture and make of motor, but you can have the other guys motor for $XX if you give him the one in your car. This assumes that the older the motor, the more miles it has been run. The amount of time and money invested in development of the motor becomes less of an issue, because nobody wants to give up something they've poured big bucks into in order to squeeze out a few more hp to gain a power advantage. If the avaiablity of crated engine supply/choices is sufficient, this would also help to curb costs and even the hp. I'm not saying this is the way to go, but just another way that some forms of motor racing have implemented to curb engine expense/costs. I always thought this would be a great way to curb engine costs in FV.
As for weight, I like the F1k=1000cc=1000 lbs. If the older FC cars that were homologated as motorcycle cars want to run at the old wieght, great, but if you convert a DB6 or something else, you gotta get to 1000lbs.