I still don't like the marketplace
If the marketplace was limited to being an auction-house, then most abusive practises would probably be blocked, as you can't sell
- from one owned team to another with multiple accounts
- your best players to a friend in a league when he's competing at the top and you are down at the bottom anyway
- for token amounts of in-game gold, while also real-world money changes hands (e.g. in high-level tournaments with real-word money or benefits at stake).
- team-members in exchange for a fixed match-results e.g. a conceded next match (although this is rather unlikely, i assume).
However, the direct sale option seems to allow all of this
Also it still needs to be seen how this affects balancing, considering the following points:
1) you can only sell players between compatible teams, so the more teams of a given race there are in the league, the more options you have, making favourite teams even more attractive.
Low-tier teams o.t.o.h. are probably out of luck (e.g. halflings, not so many halfling teams and halfling trees are incompatible with wood-elf trees (unless you award/remove "Loner" during transaction).
2) the amount available suitable players for transfer (considering skills and injuries) and available gold at a given TV, will probably be (on average) quite different for each race.