As for pure AirMechs, I don't know why they couldn't exist. They're almost there with Partial Wings.
Been doing it for over a decade. Do yourself a favor, throw out the overly complex for the simple. I prefer them, they're more flexible with more construction options and much more fun.
I do insist on the original movement costs, though; 2 to launch, one to gain altitude, ground movement Walk-1/Run-2, etc. If you insist on not counting properly, I came up with a nape-of-the-earth style (Think rocket-powered roller-skates.) to accommodate people, where they can slam into trees, sideslip, crash, etc., while I laugh heartily.