All things you've already said, Jon.
Personally, I'd actually very much like to see a Modern Award Winners category. Maybe even as modern as limited to the most recent year's awards. This would provide some of us who have been known to be a bit lazy about our reading to actually stretch a bit and read something both contemporary and of merit.
I'm not opposed to your suggestion of 3 or more "modern" categories. But, depending on what else is in the list, splitting both SF/F and M/T may not be viable, though I certainly agree that they are different. OTOH, there are also plenty of books that I'd be hard pressed to decide which side they were on of those divides.