Anyone set on using inserts could have a machine shop drill the 1/4" toe holes so they'd be positioned perfectly, they'd probably want $50 or so. If they use an end mill, they could "erase" existing ski screw holes. A vertical mill is substantially more accurate than a jig and a hand drill.
They just have to be careful to not crush the ski in the vise, and shim one end of the vise equally if the ski has a lot of sidecut to make sure it's clamped squarely.