I am thinking of a new trade metric (read "restriction") which would probably do a lot more to maintain league balance than the three trade maximum rule.
No more than three rounds movement (up or down) for any pair of picks in a trade and no more than three picks involved in any trade.
What does this mean? Well, it makes huge and complicated trades impossible. If you wanted to bail out of the 1st round, for example, you could not accept anything less than a 4th rounder for it, and nothing more in return than two seperate move ups of three rounds (with the other two picks in the deal). So, for example, under this metric, the highest possible return for a trade down out of the first round (and the most unbalancing possible trade) would be as follows:
1st, 6th, 7th
for
2nd, 3rd, 4th
The 1st pairs with the 2nd (the smallest movedown possible), while the 6th and 7th pair with the 3rd and 4th (three round move up in both cases). It is still potentially unbalancing, but I would personally find the above trade acceptable. One GM might end up with an advantage, but it would not be a league-killer.
If we adopt the above standard, all the nonsense trade bickering could be put to rest. Trades belong in the ATD; they are a very important tool that allows GMs to build the kind of team they want to build. A little move-up here to get the guy you want, a little strategic move-down there because you don't like the guys on the board...these things are good, and should remain in the ATD.
But these monster trades are a poison to the league, and should be snuffed out once and for all with a clear rule.