A sliding scale based on market price is pretty standard protocol, my bad- You right. What I thought was the kicker here is that the budget could also be factored as a set amount in SBD, I feel like that's actually a really good application of the currency, since Steem-backed Dollars are always supposed to be close to $1 USD.
Overall, I can see you did a lot of research and thought hard on the different ways SMTs can be used for referrals. The people who decide to make a token, wouldn't be stuck running their systems all the same way, and each program could be better tailored to the community it will represent.
I really hope they do this, it would help raise the value by a lot.