Have at it, ManxMan. Lots of BMW bikes running sans x-over tubes. I've heard several different explanations for the tubes, ie: improved low end torque, better exhaust scavenging, less global warming, reduces plaque build up, blah, blah, blah

Many of us are running sorta semi-missing crossover tubes due to rusted and leaking tube joints! If you plan to fit larger and more open exhaust pipes, you may need to play with the carburetor jetting.
Do post up some photos of your modified exhaust.
Monte