I use both those processes in my basement a lot of folks vaccum bag. Autoclave is even easier. I've never made a composite barrel, though I saw it coming ten years off. I always thought it would be worse for heat, apparently fine.
I think a bigger problem than the composites would be that to make a big difference in the apparent weight and performance of your barrel you need ot reduce the insert to a minimal degree, Maybe one could locate the part for relining or something. But even then one would need the barrel stub also. On the other hand, reducing a barrel on a lathe could do odd things to bore dimensions or get the "liner" so thin it would be hard to keep straight. It would be worth a try though, if one had a gun one was just going to toss the sporter barrel on anyway.