I think the premed curriculum should be two years that are standardized, culminate in the MCAT, and can be used to fulfill science requirements in other majors. That way everyone can just use the first two years to try and get themselves into a medical school, know if they're going to fail early, and switch gears having saved themselves a large amount of time. Medical school itself should remain four years. You could compress it to 36 months of you forego vacations, but that creates three hellish years and also gives students less time to explore their interests. Having medical school be shorter than 36 months would cost us global recognition at the WHO level and look quite bad for American doctors. Furthermore going from nothing to MD in 5 years would be the shortest pathway to a MD in the world, and really put high pressure on students to learn an ever larger amount of data in a shorter amount of time.
Now, with regard to training, I think GP pathways should exist that allow practice after 2 years that would be reimbursed by insurance providers. It's absurd that a NP can practice independently and be reimbursed by insurance after 500 hours of self-arranged clinical rotations while a physician gets nothing unless they're board eligible, despite carrying a full license and far more training than a NP