Qlik Sense has recently added a copy sheet feature which is great. The problem with that is you end up with 'n' copies of the original sheet spread across multiple apps - simply unmaintainable in enterprise scale organisations.
Can you think about a may to have a sheet locked as a "Master sheet" in some way, and allow other apps to include that sheet ? Yes there may be issues around different data models, objects, security etc but at least this will facilitate the creation of a single master sheet for a team. Great for templates ?