Changing keyboard shortcuts won't solve the issue of legacy styles pasting in. You will need a macro to remove/reallocate those styles when they are spotted.

On the list front, I agree with you. It makes no sense to separate the four levels into 4 separate lists. Multi-authoring is not the greatest thing ever but it isn't to blame for paragraphs losing their formatting. If the style definitions are right, selecting the text and pressing Ctrl-Shift and Ctrl-Spacebar should return the list paragraphs to their full glory.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia