First: I love your visual Toppics 
Okay I have one question about that,
If you have inactive Skills will they still lvl up? Sure you said tthey won’t bgive you your benefits because their inactive, but what about leveling up in the background? I think you could see the active Skills as booster, so they will lvl up in normal Speed while you’ll get for the inactive Skills the half of XP while you’re doing it.
I would not like to not level them up at all because that would lead you to switch the active skills every half hour and that would be annoying. Also it might be that you forget tio switch it and youre working lets say 2-3 hours with magic. You thought you should lvl up already but you wont cause you have done all in vain.