The module vanishing is not what I expected either! But backspace is OK.
Using modifier keys kind of defeats the shortcut idea of keyboard shortcuts, so I've just given up on the idea of using cursor keys. It's a pity though as one can see in VMD that cursor key shortcuts work nicely for certain applications.
I thought about using other keys but expecting users to remember weird key assignments is poor UI design. Best to just let people get up to speed with mouse , touch pad or touch screen operation even though it's always going to be slower than using keys.