Just hearing the words "trade restriction" can make a GM cringe. But we have a lot of trade activity with it. More than our allocation year when we had 3 trades per team allowed.
Edit: actually need to cut these in half cause each trade is doubled on the trade grid.
jouameng and I were discussing this last season on how it makes GM's pursuit trades they are looking for throughout the whole league instead of settling in on making multiple trades with the same couple of teams. I think it also challenges GM's to make each trade count the best they can.
If your looking to add a trade restriction to your leagues I'd me more than happy to make up a spreadsheet for ya. I'd have to send via email as I have no clue how to do it on this forum.