Not sure how much space you would get or if it would work but how about remove the outboard pad, loosen the caliper bolts to half way then push the caliper back so that you create a space between the inboard pad and disk. Now hit it with a hammer! But seriously try hitting the pad back away from the piston rather than trying to remove it straight away (you would have to push against the caliper wile you hit it), you're trying to break a rust line along 2 full edges, by hitting inwards you are only trying to break a small portion of rust.
I spent 3 hours removing a drum today i'm now an expert on rust removal 
I tried the above but ended up removing the caliper. You need to support it though if not removing the brake pipe.
I managed it without putting stress on the pipe. My inboard rear pad had seized in, both sides due to the estate being laid up for a few weeks in winter. There's plenty of crud that builds up in there, on the edges of the pad backplate. You need the caliper out really to give it a good clean in there, once you get the pad out.
Mick
