Small to mid market teams generally don't sign much in the way of FA's away from big clubs anyway (at least major ones, with the apparent exception of Seattle). The net effect would still be positive for most if not all of those clubs. All players are affected equally by it, so it wouldn't retard any player over any other player. It would simply factor in to the contract they received - which actually brings up the more serious problem that it would never pass the player's union anyway since it would in effect be taking money out of the players pockets and giving it to the owners.
The second part of the suggestion probably has a better chance of success, where teams gain extra draft and IFA cap space based on the contract the player signs with a new team (or an extension with their current team). Since the larger FA contracts are usually signed by the larger market teams / teams not rebuilding, it should cause small market and rebuilding teams to have a shot at adding better talent in a free-ish market environment. Boras would love it at any rate, and it would certainly make the draft period a heck of a lot more entertaining when moved away from it's current slot format. Offer any player any amount you wish within your budget.