Kevin,
Yes it'd certainly be tough to wait for a bloom on each seedling while they send offsets all over the place. Even now many of my 2 year olds that HAVENT bloomed have colonies about a foot in diameter! I think if you wanted to take breeding for blooms seriously you'd have to cull most of the offsets until you saw the goods. My sedum selecting has essentially been a failure for similar reasons, not only because so few of them can intercross, but also because the mounds are stringy and spread way too fast to keep track of, one might say where I've failed to make a sedum selection I've succeeded in producing sedum sod!
I've begun to cull plants in the last week that I actually like. I recently sold a large silver-yellow that was pretty nice, it had a slightly smaller sibling with more of the yellow hue and for a longer duration. The stolons were kind of ropey to, I must admit I kind of miss it, but if I allow the bar to be set that low my beds will be brimming with maybe's.
Lots of these are really nice, but there's really only enough room for the extraordinary.
-Sol