One thing I'd like to discuss: In Switzerland we commonly use the term "subskill", but I often encounter the term "sub-level" on english pages. Is subskill a term only used in the German speaking countries? Should sub-level be the main page and subskill the redirect?
Subskill is commenly used too. I've also seen sub-level skill. ;-)
I'd choose to let sub-level redirect to sub-skill.