Is it the general concensus that sending him on a trade mission a better option?
i always do trade missions. the lump sum is more immediately useful and whatever CS you do this with could mean 30+ turns of extra bonuses and get you ally status. i forget what the lump sum actually is (ive gotten 500+g in vanilla i think) but it would take 50+ turns settled to make up for it and you wouldnt get the CS bonuses. but i so rarely get GMs they are very late in the game and usually gifted by a CS from the patronage policy, that or a must choice from Maya. Ive only maybe once naturally generated one.