If you were super comfortable with sudo and commandline, I think you could work out how to do it. True there are stuff that if you remove them you might break the system. But with a regular SD-card back up, that isn’t a major issue.
I’m not comfortable with giving out “a list” of what makes OSMC OSMC, eg what you can or can’t remove without system regression. But I’m not stopping you from trying it out, get to know your systems in and outs, I mean even if it’s to much work to get “little extra space on a SD card” or “get those annoying updates” out of the way, think of the enjoyment in learning what tics under the hood.