This sounds like a great idea to me. If we want HIVE to become mainstream, we've got to do some things that make it too good to ignore. We've already got the fastest, most decentralized blockchain in existence, in my opinion. This just adds another arrow in a quiver already full of them.
While I think the true explosion in HIVE is still a few months away, I do believe it is coming, and having a stablecoin paying 20% will add a major benefit to anyone looking to get involved in the ecosystem.
Because of this, I just added @smooth.witness to my witness votes bringing him very close to cracking the top 20.