I always err toward ripping out more plaster if its stability is questionable. You will end up spending more time and money messing with it than if you just gutted all of the plaster and laff of the entire wall and then redid it all with drywall. Seems major, but you can strip a wall in less than an hour, then drywall it in an hour, then mud and tape it in a couple hours. How much time would you spend doing it your way? Twice as many? and the results won't be as good. Get Messy, get angry, get a large wrecking bar, a pickaxe and a sledge hammer and have some fun!
If you think that is nuts then you can always buy the long drywall screws with the large special plastic plaster washers to reinforce it, then just add 1/2" or however thick shims to your studs before you drywall to get it close, then use the metal laff sheets or very large fiberglass mesh for the joints and skim coat plaster the entire wall (or better yet hire someone to do it). My restorations we just get the new work "close" and the skim coat guys come in and make us look like geniuses.