Probably not of much practical help, but I believe it is possible to get a commercial airplane certificate without spending one second of time alone in an airplane and without having a medical certificate at any point in your training. Just get a private and commercial in gliders and then do the commercial airplane rating as an add-on via Part 141. Taking that route, there is no requirement for PIC time in airplanes and no requirement for "real" solo time, because the rules allow you to have an instructor on board for the "solo" flights.
Under 61.23(a)(3)(vi), of course, you would still need the third class to actually take the practical test, though in theory, you could get the medical done the morning of the practical test and never have had a medical during any of your training.
The point is, if you think you might be able to get the medical at a later date, and you are willing to spend extra time and money on a somewhat circuitous route through training, it is possible to make progress toward your aviation goals while waiting for the medical issues to get sorted out.
Nope.
141 Appendix D
2.
Eligibility for enrollment. A person must hold the following prior to enrolling in the flight portion of the commercial pilot certification course:
(a) At least a private pilot certificate; and
(b) If the course is for a rating in an airplane or a powered-lift category, then the person must:
(1) Hold an instrument rating in the aircraft that is appropriate to the aircraft category rating for which the course applies; or
So that's out because
Appendix C to Part 141—Instrument Rating Course
1.
Applicability. This appendix prescribes the minimum curriculum for an instrument rating course and an additional instrument rating course, required under this part, for the following ratings:
(a) Instrument—airplane.
(b) Instrument—helicopter.
(c) Instrument—powered-lift.
2.
Eligibility for enrollment. A person must hold at least a private pilot certificate with an aircraft category and class rating appropriate to the instrument rating for which the course applies prior to enrolling in the flight portion of the instrument rating course.
And under 61.
61.129(a)
For an airplane single-engine rating. Except as provided in paragraph (i) of this section, a person who applies for a commercial pilot certificate with an airplane category and single-engine class rating must log at least 250 hours of flight time as a pilot that consists of at least:
(2) 100 hours of pilot-in-command flight time, which includes at least...
(i) 50 hours in airplanes; and
And getting an instrument rating under part 61 requires PIC time as well.
How is the person going to log PIC time while unrated?