I am using foundationless deeps for everything, with an unlimited broodnest.
I have lots of wired frames so I leave the wire on these. I have also put lots of frames in without any wire though, and I haven't had any serious trouble yet with collapsing, I haven't decided yet, but I think my long term plan will be to wire all the new ones as they go in. Fishing line sounds like a good idea.
I put "empty" frames in the brood nest with no starter strips and they go fine, but starter strips definitely make things go smoother, especially in the honey supers.
I just cut them out of thin plywood and glue them in.
And yeah, deeps full of honey are heavy.