Crazier idea - what if the patent pool (for some domain maybe?) was fixed? (ie. there can only exist 10k patents?) Then the cost of patent search isn't ever increasing as long as rate of patenting is higher than rate of expiry. And possible it could provide a mechanism for removing frivolous patents (like - you could buy a patent 'slot' off an existing holder - so you'd be incentivised to find the most stupid patent so you could offer them the least cash upfront, as they'd not be holding out for licensing profits).