Like Gobes I have done CC touring on my Trek C1000. It has a carrier and guards on it all the time. I have had the gearing changed to MTB. 48,36,26 up front and 11,32 on the rear. This gives me a great spread of gears. THe bike handles really well with panniers. I have done some rapid descents no problems at all. THe bike should be able to take a good load . I am 140lb and some people out thee riding these bikes are 182plus lb so as you said you have at least 30odd lb for gear. If you were going to do very long tours you may want to think about a proper touring bike for the reasons stated by Mtnroads. The main thing is get out there and try it. The 1200 has rack and guard mounts , though using guards does limit tyre size, I am riding on 23s.
Cheers Brian