for planetary you'll be sweet.. but for dso's.. From what I understand (and a 12" on my EQ6 is my future plan, so I've done some reading on it) The 12" ota on its own is pretty much the payload limit. then add rings, dovebar, camera, 5x powermate finderscope etc. etc. you're pushing it.
If you were to be adding a dslr, guidescope, guide cam etc. I think you should look towards a G11.. I've seen G11's holding a 12" newt, 4" refractor as a guide scope, dslr, guide cam, 2 finderscopes (one on each ota)
The g11 is a pricey unit however... You could offset the cost by selling the EQ6... but its still a 1400 expense that I for one cant justify... YET
Edit: You'd get away with a 10" + dslr + light guide scope (something like an orion ST80 @ 370g) and a guide cam... but still a slight wind would end your night I think.