Was looking for this as well. Happy to see it's something youre considering, and thought I'd my $.02.
TLDR/Summary:
My vote would be for a simpler cut copy paste function that would allow you to copy whole pages within the same document, released sooner. vs a more comprehensive function that would allow copying between documents or pieces of a page, released later.
In terms of functionality, being able to move whole pages from one drawing to another or copying them within a drawing would be most important.
UI for this could be something like Nitro Pro's for moving pages from one PDF to another - you can see the list of pages in one file, select the ones you want to cut/copy, and paste them into another file (i.e. drawing in this case). So the cut copy paste functionality would be on the area that shows thumbnails of all the pages in the drawing.
Being able to cut/copy/paste whole pages of drawings would be most useful (at least to me), specifically in two instances:
1. You have a component, you've placed dimensions/annotations that fill the page, and have some other aspect that you need to describe, you could copy the drawing (or page would work too) and annotate the new page with the other layer of information.
2. As a way of replicating a page. You have a drawing with lots of body/components, and you're only showing 1 component. It would be great to not have to start each page with the entire model and whittle it down to the component you want to show, since this is laborious and also CPU intensive/a slow process (esp. on my laptop). So the use case here is that you have a model with 100 components, and 100 bodies, and you need to do drawings of each. component, and to annotate you need to show some mix of bodies with the subject component. Currently you need to start a new page with a full model, and remove pieces until you get the mix you need. If you could do this once and then copy and modify that page, it would be a big time saver. More of a nice to have than a need to have, but would address an issue that would have a welcome impact on workflow.
There are also some instances where you want to move pages from one drawing to another (e.g. to reorganize); probably pretty rare, but you sure notice the lack of the functionality when you need it.
To keep it simple, I think virtually all use cases for this functionality would be 90% served by a simple cut/copy/paste command, at the page level (i.e. in the ribbon at the bottom of the page). Trying to do this for parts of a page (e.g. selected items/pieces of a single page) seems like it introduces a bunch of complexity and only adds a little extra utility. It's already pretty complicated to make paste to a different drawing possible, as there have to be a lot of commonalities between the two drawings for it to work.
Creating drawings is definitely my least favorite part of the design process, so anything that reduces time/repetition on this front would be much appreciated. Thanks again for all your work on this awesome application.