YEah... a best of is your best bet. Especially since you'll wind up getting quite a bit of repeat sketches. I'd think that if they can put like the best episode or 2 per season and put them in volumes, or dual layer disks we'd have something more reasonable. Since you can fit anywhere from 3 hrs to 6+ hrs on a DVD, you could only have about 3-6 hrs per DVD. An episode per year, 6 eps per disk, 4 disks per set= about 24 seasons in one volume.
Unless you just want best of certian characters, better compiled with more footage than the current best ofs. And then there's a possible idea of a "Animators of Sesame Street" collection, with the best of each animated sketch per animator who worked on the show.
There are more possibilities for "best of" type disks than a Season set...