Sony are passionate about profit. Unless someone at SCE or higher thinks that amateur/outsider design of teams would be extremely likely to produce more profit, they will not see a need. The dlc that they did release was all solicited by Sony from professionals in the game or the famous in the art 'business'.

[waxes philosophical]> I am not trying to squash idealism, but am pointing out potential for denied hope. The designing of itself is worth the effort for the satisfaction it brings to the designers and their fans. That should always be its raison d'être. The stuff that's done only for acceptance or profit is worthless. To me.