Changing gearing has a much bigger effect on the higher gears than the lower ones. Let's say 2nd gear is good for 80mph and you make the gearing 10% shorter. Now 2nd gear will be good for 72mph, which isn't a super drastic change. But if 6th gear is good for 230mph, it'll now top out at 207mph. 8mph difference in 2nd gear, a 23mph difference in 6th gear. And that difference comes into play across the entire range of the gear, not just at the top end, obviously. Point being that I don't think shorter rear gears will suddenly make the 5BW unusable in the lower gears.
I have been thinking about buying a C7 Z06, but read about how its gears are even longer than the 5BW. I found a thread where a guy with a C7 Z06 had swapped the gears for 4.10s and loved it. I have 4.10s in my 1994 Chevy wagon, and while 3000rpm at 90mph doesn't do any wonders for interstate fuel economy (it's around 13mpg at that speed), the immediacy of acceleration is worth the tradeoff.
With the 5BW, I think the bigger problem is how much longer 6th gear is than 5th. Shift from 5th to 6th at ~160mph and the huge drop in RPM really puts a damper on acceleration. I wonder if swapping to 4.10s would make a significant-enough improvement in top-gear acceleration, or if it would just get me up into fall-on-its-face gear sooner since 5th gear redline will be dropped into the 140s.