Is it worth delving deep outside my field to revise a paper?
Do you have a colleague or someone else you can ask who is an expert in the field you need? It is possible that with expertise in the area the reviews are very minor and a one hour talk with the right person will enable you to do whatever the reviewer suggested. Even if some of the reviewers ideas do take a lot of work this should enable you to satisfy some of the reviewers requests and come up with a reason to not do the others. Finally, if some of the questions create new interesting projects this might be worth going into, especially with a new collaborateur.