Thanks for the feedback!
I considered the idea of using a token, and it is certainly an option. It would be up to the institution that was doing the implementation to decide on that. I don't have a preference one way or another, but an institution might-well prefer to use a branded token, or a token that's tailored for the specific purpose.
However, I think there are some relevant points that mitigate the risks that you describe:
(i) The concept is not just a charity. It's also an investment. As an investor, the institution would have the same incentive as every other stakeholder to protect the value of the blockchain. They would be just as trustworthy as any other blockchain user. If we want to say that we can't trust a university to post worthwhile content, we may as well say that no one should use STEEM because everyone might spam it.
(ii) Under this concept, the institution would not be withdrawing any funds at all for 10 years, and when they start withdrawing, it would be on the order of 8% of their stake per year (and that percentage would continue shrinking). This small portion should not represent any kind of threat to the blockchain, especially since the concept is to continue fundraising and investing, and (coincidentally) the cost of tuition is on the same order as the new funds that would be invested. Thus, the university's stake in the platform would grow continuously.
(iii) As noted in another comment, the fund would be owned by the university, not by students. Further, withdrawals would be performed on an orderly schedule, not whenever a student happened to experience a cash crunch.