I think the cert trade-in is a good idea. It might not be necessary to make them tradeable if that were done. I think WP has already mentioned they are against unbinding them because it may incentivize botting if they can be easily converted into zeny on the market.
Like Xellie said, the rate of getting a random cert is pretty high now. So it's really just a game of grinding til you get the one you want. A cert trade-in npc, even if its 3 to 1, would help out legit players and wouldn't help out people willing to bot. Hunting the items is enough work in my opinion.
On a side note, I would just recommend roughing out a tier 3 box before finalizing tier 2. There are some items and cards currently in tier 2 that would fit much better in the highest tier (Orleans Glove sticks out the most).