Thank you Joskin, the UID idea is something I hadn't considered and sounds useful! I'll have to try that.
However it isn't really a replacement for the ability to piece objects together at design time in a prefab/template style. The ability to nest objects at design time to create composite objects is a very powerful feature that would benefit many Construct 2 users, but I have no idea how difficult it would be to implement on the dev side. It is probably quite a bit of work.
Still, if I can't find a way to do it soon, I'll head over to the general discussion and request it as a feature. Can't hurt to ask, right?