Repair basement stud walls after french drain
I would do exactly that using PT lumber for the plate and the extensions. You'll need a powder load gun to fasten the plate to the concrete. I would cut the extensions to go under the existing studs (tightly) and sister a piece to tie the stud and extension together. How do you plan to fix the wainscoting/paneling? My guess is you will probably end up tearing all of that off. In which case--it may be simpler to replace the entire stud (depending on how the electrical/plumbing is routed)?.