this is currently debated in the CU thread
you may leave an opinion there - because there will be a finalization
but so say a few words on the subjects
planet trading could be done quite exploitable, the AI routines are erratic & gimped, but we couldn't change these...
traditional farming, and esp. bonustiles, sometimes lead to extrmely high maxpop planets which the AI can't handle - it'll wreck his economic game. thus, all farm projects gave a % instead of a base food bonus, as such bonustiles became irrelevant and were made invisible. I think it's currently changed back because the AI doesn't reckon farms as being farms, currently.
the farming problem is somewhat impossible to solve without any drawbacks on some regions....