This is exactly what I do these days - but then, I'm not a honey-farmer with massive flows going on around me. It's a tip I picked-up from the Natural Beekeeping guys - I first tried it with a KTBH (which I later converted to deep frame), and found it worked so well that I decided to stay with the method. I've now settled on 4 holes for brood boxes, 2 for 5-frame nuc boxes and 1 for mating-nucs. Adjusting, fully closing or transporting has now become a breeze. It's a particularly good method for anything non-standard - like divided boxes, or queen castles.
Most of my boxes have these holes near the bottom, but I do have a couple of 'specials' which I use together with a turntable for queen-rearing, with holes at both bottom and top, so I can then swap entrance positions easily.
Personally, I wouldn't change from this format - but then I do make most of my own boxes, so that they have minimal re-sale value. If I'd purchased uber-expensive cedar boxes (or was a serious honey-farmer), then I'd probably have stayed with the standard configuration.
LJ