Well, the more I look at things, I think I might have to tone it down some. I do NOT have a use for a rider. I think that would be the better way to go, yes, but that's just not in the cards, I don't think. What I have come up with is something less spectacular, but still out of the ordinary for a push mower.
I've come up with these two:
Tecumseh 10HP single cylinder
And this one:
Briggs & Stratton 10.5HP single cylinder
Other ideas you guys?