Repairing Plaster Walls

We were unlucky enough to have wallpaper on every wall in our home when we purchased it. However we were lucky enough to have all of the original plaster walls (in our opinions this is lucky). The problem is that in some places the plaster was literally being held together by the wallpaper. Even before signing the closing docs we knew that at least one portion of a bedroom wall would have to be replaced completely with either new plaster or drywall. In another spare bedroom we recently decided that portions of the plaster were not stable enough to stand the test of time. We removed large portions of the plaster (enough to fill three tubs shown in the right hand picture). We looked into having the walls re-plastered but for all the work we still need to do on this house we just feel it is going to be too cost prohibitive. We're going to incorporate drywall into these walls with the remaining plaster. For us, not the ideal solution but one we can feel comfortable with.