The Green Goblin has identified one of the biggest problems.
From a practical point of view, all the skills requirements of the Manual of Standards would be covered in a regular instrument rating/renewal/proficiency check on a multi-crew, turbine powered aircraft and this would ideally mean the form could be filled out, and an ATPL issued. However the applicant "must perform the functions of pilot in command" - Manual of Standards Instrument 2014, Vol 1, Section K Appendix K.1 Para 1.5. It also has to be from the left hand seat.
So for all the first officers at smaller operations hoping to gain an ATPL and move on to bigger and better things, this holds you a hostage to completing the check and upgrade process within your existing operation. If there arent upgrade opportunities, you cant or dont want a command in your current job, fail the upgrade or have upset the management and wont get an upgrade you are effectively trapped with that employer while the larger employers or overseas ones arent interested in you without the ATPL. I doubt that your current employer will just throw you into the left hand seat for a few sims to help make you more employable elsewhere. That'd be a fun conversation to have with the manager...
What has been achieved for those outside the airline system is a massive increase in the costs to gain a license. Inside the airline system, the licensing is now at the whim of a check and training department with no incentive to help you become more employable elsewhere.