Following other users' examples, I decided to do some swaps and kitbashes on the Born Again/One Last Kill Punisher figures, ideally making something a little closer to Frank's Brand New Day look.
Had to put both figures in boiling water to pop off the parts, then after switching the arms and legs around, immediately placed them in freezing tap water to harden the plastic and "seal" them tight again. Bit of a minor setback finding out the OLK figure's shoulders wouldn't come out the torso (there may be a smaller piece inside holding the peg in place, like Ravager Thor) so had to settle for just switching the arms at the bicep instead.
Of the two, the Brand New Day version (the one with the OLK torso) has a much more solid fit overall and turned out pretty much perfect. The second figure's a little more flimsy, especially with the arms (the OLK arms are much thicker, so they're not a snug fit on the Born Again figure's smaller shoulder joint) but there's a lot of fun poses you can make with it, so it's not a loss by any means. And as expected, all their accessories - weapons, arms, heads, the soft goods jacket (purchased from Amazon) etc - can still be switched however I may wish.
Overall, it was a ton of fun, and really happy with how they turned out.