As you are not playing your best players as start players twice a week as well as you might play them out of position for both game shape and training reasons the MVP award could actually be to a pretty average player. -- -- For such reason I think that the MVP award are not reasonable to use as a criteria for sponsor money and similar issues.
That, however, would essentially be a strategic choice: do you go for the maximum benefit from training or sponsors/merchandising. Generally, a choice which is obvious (such as, go for maximum training AND sponsor money VS. choose to not take money from training and/or sponsors) is not a real choice and adds absolutely nothing to the game. It's better to not have such options available since they only make the interface more cluttered which is bad especially for those who spend little time in the game. (Of course, some choices may be simply for fun and are therefore beneficial to the game.)
Overall, I think it would make the game more fun if there was a stronger incentive to play your top guys night in, night out. Balancing training minutes, game shape, and often playing your best players out of position is a challenge, which shouldn't be removed altogether, but there should perhaps be better options to that model.