I’m not really seeing a way to satisfy your requirements honestly since the controls just simply aren’t designed to work like that. To play GD and get the full benefit requires use of both mouse and keyboard in tandem (unless you go controller - which works pretty good for a game of this type even if there are some limitations).
The only thing I can think is that maaaaybe something could be done with AHK scripting to make what you want possible. @tqFan would be the one to know that.
As you can see here…
…it opens up a lot of various possibilities for modifying your control scheme.