Currently working as a corporate consultant. I have recently found out that I am not fulfilled in my corporate career after taking a 6yr hiatus from building my flight career. I am 30yrs old with 600hrs total with multi-commercial rating/applicable endorsements that also earned a grad degree recently. I know there are several different paths I could take to close the gap to 1500hrs (CFI, Dive pilot, towing banners, etc.) Any advice for a guy like me looking to get back in aviation and into a regional FO seat?
You really answered the question yourself. You need to build the required hours and you know there are various ways to do it. Get current and start investigating opportunities in your area.
I would strongly recommend that you pursue the CFI route, CFIs tend to be by far the most competent pilots when it comes time to switch over to airline training as their skills and knowledge are generally pretty sharp.
It isn’t just about getting to 1,500 hours, making it through airline training obviously maters as well.
Get current, get an Instrument Rating (if you don’t already have one), and find a job, preferably in a multi engine turbine aircraft operating under IFR rules.
That or become a CFI and teach.