That's a pretty significant goof on a $3/4M yacht... I'm fairly familiar with Beneteau's grid structure architecture and it seems completely possible to drill limber holes at the appropriate intersections but it is more complex than it sounds;
- the simple way to descried it is to drill slightly oversized and epoxy in a short length of G10 tube
- problem 1 as stated above by
@Captain Ag is that the hull liner does not always have an access panel at every intersection of the grid structure. To get all of them you'd have to cut access panels and that is not pretty.
- Problem 2, nothing is at a perfect right angle on all dimensions where the limber holes need to go. A long drill bit will not track straight through and parallel to the curved hull at the athwart ships intersections. It will also not track straight because the of the size of the drill chuck and tool body, but I could probably work around this. The very bottom of the tube needs to be flush with hull surface (which slightly curves) so that no residual water is left on the 'upstream' side.
- The best solution I can imagine is attempting to pilot drill each limber hole with a small diameter bit from two sides (which is probably not possible at every place covered by the liner), and then use a carbide burr to enlarge the hole... Its a mean tool that eats through glass like butter but also requires a very good eye and steady hand. If the hole is shaped correctly then a short length of G10 tube can be inserted with thickened epoxy. I'd actually also cut the very bottom of the tube off (longitudinally) to get it flush with the hull.
Anyway, materials cost would be very low, but labor could be very high. If sections of the liner need to be removed to create access, we are talking serious fiberglass and gelcoat repairs as well as replacing the cabin sole wood covering. This isn't a job I would expect an owner to tackle DIY. Major gaff on benny's part.