I suspect a neater split might be "biographical" and "non-biographical" - we have 2350 FAs, of which 550 are biographical; the number of biographical FAs seems to be growing at 15-30 a month, and they're generally speaking a topic that lends itself well to a one-person drive to get to FA status.
That's not a bad idea - "Today's featured biography" and "Today's featured article".
On the other hand, I don't think we need such a split :-) We're not under any obligation to show every FA on the front page - indeed, even if we do ramp up the number featured at any one time, we'd likely get ahead of ourselves again in a year or two.
True, but I think it would be nice for those people writing FAs (I'm not one myself) if they got them on the front page, and got them there sooner.
Perhaps rather than having any formal two-stream system, we should just do what DYK does and increase the frequency of updates? Running two FAs a day might be simpler if we just changed over at 00.00 UTC and then again at 12.00 UTC... but then we'd have to stop calling it "today's featured article". Hmm.
That could work, but the problem is that people who only check the front page once a day (which is probably a significant group) would miss half the featured articles. I think if we were going to do that we would still need to have two articles showing on the front page at a time. "Current featured article" and "Last featured article". If we're doing that, though, we might as well alternate between two categories of article as well. Having the article from each section update at a different time would be good, though.