One question I have is:
Do you have twenty “Good” years? Are you retirement-eligible right now? Okay, that’s two questions, or one and a half.
As you are already flying 121, and are already a graduate of a military flying training program, the more time you spend playing with Mother Green the longer it will take to get to your dream legacy or that 40+ continuous years of profitability B737 operator of choice. Every drill period or Annual Tour, or deployment that has you drop 121 trips will delay you to your destination. And time spent NOW not getting closer to your destination will cost you BIG bucks in final salary and retirement account LATER.
The retirements and hiring are ramping up now. Get upgraded, get 121 PIC, get your apps in ASAP; you don’t know who might call you in, or when, to interview.
Now if you are dead set on staying in the Guard, do it. But I would caution you on chasing the C-12 to improve your resume; it doesn’t seem you need it. Regardless of whether it was as WO, O-4 or O-5. The time spent getting qual’d, then seasoned, before PIC, is all time better spent logging 121 hrs.
What is your rationale for “five years until full transition” to pure civilian life. If you need that to qualify for retirement, good enough. If you need a year for O-5 selection, a year to pin, and three more to retire in grade, do an assessment, and decide if that would truly be time well spent. But that is your decision to make. Full Disclosure: I stayed Blue longer than I needed to, but personally, it was worth it.