I agree with all the “or’s” but I have found it is better than having a bunch of “and’s”.
As you outline your journey for those who will consult this thread in the future, as I view it, they have three optional pathways for them to follow.
(1) In service option - Get a merchant mariners endorsement or license some where in your military mid-career position and build on while in the service.
As a engineer consider qualifying for:
(a) qualified engineering ratings e.g., National QMED and STCW Ratings and
(b) any engineering officer positions you qualify for or can qualify for while on active service and holding a MMC. Keep in mind that some positions may require training outside the military training structure.
This recommendation extends also to deck positions.
While in the service get all of the USCG Approved Military Training you can e.g., command essential training that is USCG approved or getting possible TAD orders to approved schools outside the command structure, then complete as many of the STCW shipboard assessments that are appropriate and related to you M2M goals.
Develop network resources that are familiar with USCG test procedures and potential examination topics and question styles. Look for ship’s officers that have attended the maritime academies. They may still have their USCG License Seminar Notes for Engineering or Deck.
(2) Getting Out - one year before departing collect copies all of your military records, the names of fellow service members that can provide assistance after you leave. Complete the USCG Application for everything that you qualify for. Start preparing for the credentialing/examination phase of your journey. Consider the possibility of attending a Maritime Academy. Start networking!!! Especially those ship’s officer that have attended the military academies.
(3) Retired / Been out for a while - File a Records Request SF-180 and look for assistance from reliable M2M resources.
Lastly scan or place everything you encounter on a thumb drive. Consider it as your Maritime Profession Briefcase. You will find it one of the most useful tools in design and maintaining your career from M2M.
Watch the expiration dates on your training certificates. They will vary depending on the nature or purpose of the course. Some have a one year expiration date which means you need to fill out a USCG application and get it on your MMC.
Hope all of this makes sense.