I was gonna edit my other post, but this ended up being really long so I figure I will just do it as a post on its own:
A good Subs team for me would be:
Rainbow Girl
Porcupine Pete
Kid Psycho (if Crisis never happend in the new DCU, why not?)
Polecat
Ron-Karr
Antennae Lad (give him Dream Girl-esque control over his power so he CAN call on it specifically when he wants to, but it's still prone to just kicking in randomly every now and then as well)
I think it's time for Infectious Lass, Stone Boy, Color Kid, Chlorophyll Kid and Fire Lad to move up to the main team, they've paid their dues (well the boys have, but if you don't love Drura you must be dead inside).
Even if you don't go the 5YL route and give Stone Boy the ability to move in his stone form, there are still some cool stunts you can allow him to do just by having more exact control of his transformations.
I also wonder, considering that his stone form is a hibernation mode, does he need to sleep as much as a normal human otherwise? When Zwennites go into hibernation, is that the ONLY time they sleep? Could he conceivably function at peak capacity for months on end? Does he have some kind of ridiculous level of stamina that only Daxamites can outmatch? What are his mental defences like if he can stay awake for 6 months at a time without going nutty from sleep deprivation? Would Imra have more trouble wearing him down if he really sets his mind to resisting her?
All just brainstorming, but I don't think it's hard to create advantages of his power that outweigh the disadvantage of him being immobile just by putting a bit of thought into it...