Storyline templates for team use.

Sharing a template across a team should not be an issue, but you identify a possible behavior that could call into question what your team believes a template should be used for. Perhaps I don't see why a team would try to change the slide size to which they have applied a team template; that would pretty much rule out "using the template," to me. And certainly, changing the slide size would impact anything that existed on that template, including any motion paths.

As for copying layers - I have often copied layers from slide to slide within the same project, and occasionally copied slides (including layers) from project to project successfully. However, because of how layers work with regards to being attached to a specific slide, I do not think you can copy layers separately and then attempt to apply them to a new project without creating both performance and layout issues.