KD/everyone,
I think that way is a bit more complicated than it needs to be. Let's say you and I agree to a 1 for 1 deal, but we both agree that the guy I'm giving up is slightly more valuable than yours. We could add a swap of my 10th for your 9th round draft pick, to make it an even deal. At that point, though, I wouldn't be able to keep 30 players, since I would have to drop 11 in order for my 10th round pick to exist in order for it to be traded to you. Basically, it makes it harder to trade low draft picks, unless you are planning on dropping more than 10 players.
The way we do it in our other league, which is a bit simpler, is as follows:
You make between 10-15 drops, and get that number of picks, to do with as you like. If it comes to your pick and you have a full 40 man roster, it disappears. If it's your turn to pick in a round and you have less than 40, you make a pick, up to a maximum of 15 rounds. That way, you don't have to worry about trading lower picks earlier in the year, and it also allows trades during the draft. It involves less record keeping, as well, since we wouldn't have to go through everyone's low pick trades to ensure that the picks would exist, and force people to make more drops than they wanted, due to a deal they made last September.
Anyway, let me know what you guys think.