Could he sell it to someone else for the same amount or more than charging standard interest on his loans would cost the club? If not, the suggestion isn't weakening 'the bottom line' particularly.
Not that I think the idea makes much sense anyway. As said, he is free to charge interest or take back the loan anytime he fancies, but thankfully he seems happy to get the club back on its feet first.
I'm sure if he could get outside advertising in that would get a better return than the unquantifiable gain plastering Sports Direct everywhere gets him, he would.
That's kind of what I was driving at. People seem to criticise Ashley for not selling the sponsorship to third parties, but the implication from your answer is that he would if he coule - the return just isn't good enough.