Complications to consider throwing at your players:
1) Who controls the distribution channels and rights for such merchandise? By making and selling merch, do they risk getting a visit from some of the Bertoli Family's gremlins?
2) Many of the major fighters probably sign restrictive endorsement contracts. The focus of an adventure might be to try to get an up-and-coming fighter to sign a contract with your group to license his/her likeness for merch.
3) What if you make a warehouse full of "Grady Kiefer" commemorative plates and then your boi gets hit with a major scandal, such as being caught taking bribes to throw a match? What do you do with millions of C-bills worth of unwanted merch?
4) How are you getting these into the fans' hands? Selling through gift shops and emporiums? Out of the back of a Hetzer parked in an alleyway near Steiner Stadium? There might be some hurdles to overcome in the marketing department.