A little background: I got this idea from the teamhacksung i9000 kernel. That phone has a combined boot/recovery partition (just one of the strange and proprietary things samsung does), so there are no worries about matching the main and recovery kernels.
No, jb is not that much larger than ics, and cm10 may well squeeze on there. But I'm already removing things to make ics fit. And aokp ics has already lost SwagPapers, so aokp jb may not even fit at all. And aokp is just as popular as cm. I really don't want to stop building it.