Have you tried making Custom Shows in your big presentation?

Slide Show tab > Custom Slide Show > Custom Shows > New.
For each custom show you can select the slides you want to show.
A slide can occur in several custom shows.

Afterwards, to present a particular Custom Show you go to Slide Show tab > Custom Slide Show and select the one you want to present.

or

You can add a 'menu' slide to the beginning of your major deck, with hyperlinks to every Custom Show.



Either way all future content changes need to be done only once instead of five times