A Question About The Future

Currently I'm working on A Sidekick's Tale (that will so not be the final title.)  It's going slow, and I find it's a book that is inspired by working on other things as well.  If I were to do a non-Penny book in Penny's continuity before the original series ends, it would be set pre-year 2000, and have an adult main character.  Is there anyone or anything you folks are interested in, to help direct my inspiration?