1500 hrs and a pulse gets you hired should get you hired at a regional. Suit, haircut, smile, goes a long way.
You'll be a better pilot if you're a CFI. Being a weaker pilot ISN'T a good idea going into a regional airline training program. Put everything in your favor vs trying to take shortcuts. Starting your career out with a training bust, or getting fired, would be a tragedy.
What's a 150 cost per hour? $50? That's $60,000 you'd have to fork over in 18 months to get to 1500 hrs vs getting paid $40K(1.5 yrs CFI pay?) If you had your FF job every single net dollar would go into flying. A CFI job would get you the time for free and you'd get to keep the net pay as well as getting you better prepared for your future.
More important the then the student/instructor relationship, which is important, is the quality of your training and the time delay. And you learn different things from different instructors. On the civilian side, through my comm/instr, I primarily flew with one CFI...and then he left. USAF? First 19 dual flights was restricted to two IP's. Next 23 training flights? Ten instructors! Once you learn the basics the USAF decides an instructor is an instructor. T-38's was the same, two IP's for the early portion, then 8 IP's after the basics were over. Think you have much of a student/instructor relationship when you fly with a guy once or twice? Nah. Learning objectives defined, briefed, demonstrated, flown by student, debriefed. Next.
That doesn't mean you might get a bad apple as an instructor. Don't accept that. At a professional and well run school the mgt shouldn't tolerate poor performance. You probably won't be the first student to complain. I learned and logged time which got me closer to my goals with guys that weren't my preferred guys to fly with. It's about advancing the ball.