Only if you were a complete fool. Why would you enrich memorabilia brokers for nothing in return?
The real actor in our hypothetical scenario is Johnny Manziel, star QB at Texas A&M and last year's Heisman Trophy winner. In January of this year, Manziel signed over 4,000 items for three memorabilia brokers [ref].
Even if Manziel didn't get paid (yea, whatever), NCAA rules require student athletes to make every effort to stop the sale of products featuring their likeness [ref]. Signing 4,000 items for three brokers is the polar opposite of "every effort to stop" — it's an extraordinary effort to promote.
I enjoyed watching Manziel play last year, and would have enjoyed seeing him play this year. He is an incredibly talented athlete. But given the information available at this point, I'll be completely surprised — even disappointed — if the NCAA doesn't strip Manziel of his eligibility.
You may believe that Manziel should be able to make money from his fame while he's an NCAA athlete. I won't debate that point now, as it is irrelevant to the ultimate disposition of the current situation. The fact of the matter is that there are NCAA rules in place, and while those rules exist, athletes that violate them should be held accountable. Any other outcome would be unfair to the thousands of other athletes that do obey the rules.
Not punishing Manziel would also be unfair to Manziel.
If you've followed "Johnny Football" Manziel at all, you know that he's a guy who has allowed his physical gifts and fame to go to his head, who doesn't respect rules and boundaries very much [ref]. Having to sit out a year of eligibility (or more) could be the wake-up call he needs.