Obviously what I've been doing isn't working...
Well, for what it's worth, I think in almost any other D.IV league you would have promoted by now. You've run up against a very strong team all 4 times and perhaps gotten a little unlucky in some of those. I know 2nd is heart-breaking but keep in mind you were only 1 bucket away from promotion and have set the standard for consistency in IV.28 so what you were doing was working to a fair extent, it just came up a tad shy. I wouldn't scrap your entire team identity, rather just try to improve your salary efficiency and keep doing what you're doing.
Good luck with the new direction and I'll be rooting for it to pan out and you get that promotion you've been so damn close to for so long.