I think we deliberately made it framed by default because at the time it seemed most didn’t want the interface’s CSS spilling into the template. It is hard for us to gauge which would be the more common preference.
Do you commonly have pages inside your templates that need the normal interface styling applied to it? Or is it that you want to author the CSS for all your templates in the Interface’s CSS (the alternative being authoring it within each template)?
(As an aside, pages-within-templates-within-pages seems to be quite commonly used even though we didn’t anticipate this. In case it removes your need to use this complex arrangement, we have recently added a “List by Subpage” widget to 2020.1).
Regarding your second point about wanting to change the default wrapper, we do love that idea. We appreciate that this would save you time and makes it easier to create consistency and easier to make changes across the board from one place.
Our hope has been to provide this facility in a generic way such that any setting’s default can be set globally. This is a large task and isn’t scheduled to be done in the foreseeable. If it really is just the presenter and wrapper that users need, we could get just implement settings for these. Further thoughts on this welcome.