Exactly why you haven't seen this in roms yet.
The potential for a user messing it up is quite high. It's fine for those who know what they are doing somewhat, but look around at how many have trouble with recoveries and rooting. It's just a huge amount of support most don't want to deal with.
Most of us do this in our spare time, just fooling around. You have no idea the number of requests for special builds and features we get, not to mention pm's asking for help. I don't want to be responsible for someone wiping out their entire phone. Or worse, bricking it due to a bad partition. Mmmark111 already bricked his by messing with partitions, now imagine a noob trying to do something like he was doing.
If you want something like that, great, but I already looked into it for Aphrodite and from everything I have seen, there is no way I would implement that at rom level.IF it can be done more safely and easily, yes I would give it a go, but it woudl have to be dead simple and reliable as all heck.