I like the idea of replacing exclusive rights w/ licensing rights.
Require patent filer to assign their own licensing costs at the time of filing the patent (have to exhibit some idea of the value of their invention). Then, require them to pay some multiple of that figure on a monthly/yearly/whatever basis in order to ensure enforcement of the license (so that they can't assign huge value without being able to pay for it themselves). Next, every period X increase the cost to retain the patent by some multiple of inflation or order of magnitude so it keeps getting more expensive to retain the patent (to encourage the invention to be released to public sooner unless it turns out to be hugely profitable). The early period should be cheapest for inventor to retain, and quickly get more expensive... want to keep the patent, then you'd better profit off it.
The more profitable the invention, the more likely folks will pay for licensing rights. The less successful the invention, the more likely the inventor will not renew the patent.