Without a magnetic field wouldn't this new atmosphere be blown away by the solar wind? If so, it seems a little irresponsible to propose melting the poles. It seems like a better idea to dig deep and build cities under the surface.
I am also no expert, but from what I've read, probably not in the long term. It's commonly believed that Mars used to be more Earth-like, but the deterioration of its magnetic field caused its atmosphere to seep away into space. (Mars' gravity is also just generally weaker than any planet except Mercury.)
