All proposals for single payer at the Federal level call for the elimination of for-profit hospitals and large clinics. All proposals (even the state level) call for global budgets that separate capital from operational budgets - which means that the single payer system would control major investments. If an area did not have enough hospitals a single payer system would provide capital investments to open some - probably by funding new hospitals. If an area had excess hospital capacity it could force the lesser quality hospital out of business by starving it of funds. In terms of specialists in screwing payers, it could limit the number of such employees as a condition of eligibility for funding. Also the simplicity of the billing system would tend to reduce the margins for that kind of game playing.
A single payer system gives you monopsy, and control of capital investment by the single buyer. In essence providers, while nominally independent, become branches of the single payer system. So single payer is not a compromise. The only part that retains any true independence are the smaller private practices. France, for example has a single payer system rather than primarily a national service. Yet France's health care is some of the best in the world, and while not as frugal as (say) the U.K' s national health still constitutes a comparatively modest percent of GDP.