I’m not 100% sure I understand what you want to do, but based on what I think I understand, I imagine you would use additional Types for each unique set of fields, and relate those to a parent type. Yes, you might end up with a lot of relations and a lot of fields on the parent Types that are not always filled out. That is a problem I hope will be solved with [Polymorphic relations] When creating relation, ability to have entire App from which to choose, and not just Type or something similar in the future.
Sharing of Apps is coming/in beta, and sharing of whole Workspaces too, I believe: CHANGELOG: September 10 / Apps Sharing (beta), Lock in Whiteboard & many bug fixes