I have a p944 that I picked up as a fixer-upper. Currently in the process of mirror polishing the slide as well as some of the internals. Outside of the hogue rubber grips, I've run into the same issue. You can switch out sights but that's about it. As a side note I actually have an extra set of hogue's that I'd be willing to give you. Send a pm if you're interested.
I've heard and seen some picatinny rails that can be drilled into the frame for light/laser mounting but that's not something I'd ever be interested in. The other things I've considered is getting a red dot mount instead of the rear sights and extending the magwell. Pick up a couple 20 round mags and you have yourself a kick ass range gun! Lol. Will update as the project progresses.
If you've got one foot in yesterday, and the other in tomorrow, than you're pissing on today.