I think I'm a tad bit confused about this whole thing. Which one of your players is so dominant that you feel there is nothing left to put SPs into? I am by no means trying to call you out or something, I just don't understand why 15 SPs seems so unappetizing to you. I can't think of a single position in this game where I could be in the high-20s/low-30s for levels and even be halfway satisifed with a build (especially slow builds).
True, every position has a couple of main attributes that it helps to jack up early (some positions obviously more than other), but I have a few players at 50, 49, and 49 respectively, who I have so many more ideas for as to where to allocate their SPs. Do Veteran Abilities and equipment help a little once so many attribute are past medium caps and beyond? Absolutely, but even when my players start having their attributes decrease after ten seasons, I will never not have something to do with SPs.