I think your idea is better as a token of its own. There are already several charity tokens in existence and once SMTs come online you can leverage ICOs and its own inflation design for your purpose. However, Steem is like a universal social media platform that is co-owned by all users, as such it is a business. There are two parties, curators and authors, and curators invest in STEEM and share it with authors only when authors prove that they have contributed value to the network.

Authors are worthy of a share of STEEM only when they make the network and thus STEEM itself more valuable. Steem is very much a for-profit design and charities can actually cause downward pressure on its price. How so? If STEEM rewards were going to a college student fund, those students would be having to sell off the STEEM to compensate the schoool in the currency of their choice, resulting in downward pressure to the STEEM price.

The price of STEEM is the most important thing here, because Steem is first and foremost an investment as a commodity money and a business for those owning enough of the network to be concerned with its price and liquidity. So, Steemians would want to know how value was returning to Steem, not just, potentially, a decade later but immediately.

Charities benefit from tax deduction rules, and businesses would rather donate, deduct and receive social recognition for being charitable than just give it all to the government. I think the flaw in this idea is that I see no incentive model for the Steem network itself, certainly not an immediate benefit.

There are charity designs that work because they drive adoption, immediately. For example, let's say you made an SMT and motivated caring people to contribute value into your SMT and the inflation went toward students. Some Steemians might contribute STEEM toward your mission if via the SMT inflation it onboarded many college students regularly.

Let me provide an example... Let's say you created "Essay Token" as an SMT and people could spend their STEEM to obtain "ET" that they could stake and curate posts from students presenting their essays to the community. In turn, some campus adjacent shops agreed to accept those tokens for reduced price on their products. This benefits students living on a tight budget and benefits the businesses by likely adding traffic to their shops and some STEEM can even be earned from the ICO and general exposure to the whole of the Steem community.

I think something like this ultimately needs to become its own token, not a project taking a considerable chunk out of the reward system, which is competition-based for the sake of building network value. Charities doing things like spamming the blockchain with "Support The Whales Request #194,813" with the same copy pasta on all the same posts just isn't helping Steem grow, its parasitic in nature. I'm not saying that charities are not good things, they can be, but I think they would do more harm than good to Steem by trying to siphon out value from the universal reward pool unless they are providing immediate value to Steem in some way.