[Gwaihir]

doesn't look like it, but of course you don't get much trade benefit, and since the proposals take a turn to send, there's a gap turn - would mess up the ability to cooperate militarily. Also, planets lose happiness very rapidly (so you'd have to keep doing this to keep up) when they are at high levels, unless you have Urban Pac centers, which kinda makes the treaty jockeying redundant anyway.