I don't agree with commander lvl being used because I think it's a bit high, I'm at 40 but can only just clear lvl 40 maps and that's normally with a few lost tanks assuming good RNG, with bad RNG I fail at some, thus making these 'invasion' missions not worth the effort. If the rewards scaled with commander lvl as well (say 1 candy per 5 lvls, 1 core per 10, 500 metal / gold per 10 or something) then they would actually be worth it.