Howdy!
With VRchat importing custom avatar and animations is free, easier and has more possibilities than Second Life currently. Same goes with making different size variations for avatars (you can simply just scale your pre-existent avatar and re-import it instead of messing around with any extras).
I think you should consider these same possibilities too. Especially the size changing. Would be lot easier to adjust your whole avatar's size with slider or something than having to make duplicates for all sizes. For all three forms of avatars: prim, mesh and Bento