Activate Back/Left/Bottom Viewpoints without using 'Ctrl' or 'Num9'

Hi there!

I wish for a simpler, quicker way to loop between viewpoint pairs. It would be nice if we could loop between Front and Back viewpoints by just pushing the 'Num1' button repeatedly , the same way as we can change between the axis of movement pressing 'x' repeatedly after we start moving an object by pressing 'g'. I hope for it as a default setting.

((By the way the usage of 'Num9' can freak out easily. When pressing it too quickly it can stuck in "User" viewpoint. Probably 'cos while "swap-animate" between two viewpoint the 'state' of the viewpoint become "User" for the duration of the "swap-anim", or I just don't get its real function, maybe it is just to orbit around a selected axis in 180deg)).

Thanks in advance, kca