Please change this so that they can, as you're giving with one hand and snatching away with the other.
Purists won't use then anyway. They are easy to monitor and the lack of the marketplace can be worked around making the ban pointless (the workaround is not really feasible for regular use as it takes hours).
It can't be that tough to add?
Preventing mixed or custom teams from being used by private leagues to their full capabilities is madness.
I kinda feel like the option to allow interracial trades would have been a better addition than allowing the creation of mixed teams. There are logistical problems, I'm sure, but at least teams would be limited in the team they could build by what others in the league are willing to give them, and what price.
Surely there is no reason to restrict mixed teams in this way. The whole game should be open to them as it is for the pure teams. The system as it stands is open to all kinds of farming options, the concept of mixed teams is "broken" as they should all suffer from animosity (presently the underworld teams are penalised in a way that effects no other team) so why draw a line here? Please fix this so that mixed teams can also benefit from the market place