The problem he would face is approximately the same one Obama faces, I think. The fact that it is not simply the Senators that he would have to get his ideas past, but also the deeply entwined Corporate interests of the US Banks and Stock Market, as well as probably not sitting too comfortably with the Military or Environmental lobbyists either.
Without being prepared to at least make a few sacrifices to earn external support, I think he would have a hard time getting anything done. Not his fault personally, any more than Obama is really to blame for his failures, but that is what the system has become. Ron Paul is an idealist, and I actually think on some subjects he genuinely understands the US Founding Doctrines far better than most Senators, but if he gained the power of Presidency, I don't think he would be able to do many of the things he feels need to be done. He would, I think, end up in much the same boat as Obama, crippled by Bureaucracy and left with a lot of voters who feel vaguely disappointed.