The SIG’s were formed within CA because their were groups of people with a common interests that weren’t really big enough to be a committee or likely to get any Space allocated so they organized and have a lot of autonomy, storage space, and some funding to get started, under the the Chair - which I’m sure will continue. Small Metals and Jewelry was basically a SIG that was able to get Space so they could work and broke away from CA. (Not sure if they just out-grew the nest or were kicked out). Costuming & Props (Cosplay, Punk, Anime, etc. is starting back up again under CA after halting first attempt).
The Amateur Radio at one time was a Committee but devolved into a SIG under Electronics. So things are always changing.
My advice is find a committee that will “sponsor” your SIG then you can operate something like a mini-committee under their umbrella. Go for it.