I haven't seen a pintler in person, so I'm not sure how stretchy the fabric is in that area, or what foam their using. I imagine there is a way to get into the sleeve where the foam is and you could try to replace/add with a firmer pad. XPE that seattle fabrics sells would be a good choice. Very dense and closed celled so it won't hold water.
Is it possible to completely remove the lumbar pad from the frame/bag? or is it sewn in?
OV innovations makes an add on Lumbar pad for the NICE frame. I don't know if yours is a newer guide lite frame or if they are compatible with the new frame. I have one that I would sell if your are interested in trying it out.
It is the guide light and no they dont make one for that fram. I havent checked yet ro see if its removable but i doubt i could add more padding to whats there without it being a whole separate piece.