The question of whether training more doctors is feasible is tangential to the point that making a moral choice won't make medical services less scarce. It may not be feasible, and in that case there is no solution to the problem of scarcity of medical services.

Regarding increasing the number of doctors: plenty of people want to be physicians. In 2007, 42,315 people applied to medical school, but only 17,759 were accepted.

http://www.aamc.org/data/facts/2007/mcatgparaceeth07.htm

The people who are rejected are fairly close in scores (GPA, MCAT) to those who were accepted and there is plenty of overlap between the accepted/rejected distributions.

Let me do a little normal-distribution-fu. Assume that MCAT VR of 8.3 is the cutoff for "intelligence and talent to do it well". If we accepted every white person above that cutoff, we could train about 10,728 more white doctors per year and a few thousand more asian doctors.

(I picked 8.3 so I can call you a racist if you say you want a higher cutoff. ;) )

Regarding point 4), I agree.

In any case, while increasing the supply of physicians may not be feasible, this doesn't mean it is the case that making a moral choice can cure issues of scarcity.