OK, so sleeping bags are well established but what about suits? I turn a lot in my sleep and find bags restrictive. Thought theh might be a good alternative in warm weather which seems more frequent these summers.
Are there merits in a sleeping suit? I don't recall any threads on these in this site but surely someone has tried them out (Panda onesies aside)
I seem to recall reading some while ago about a team climbing Mt. Vinson who decided they might just as well sleep in their massive down suits and save the extra weight and hassle of hauling sleeping bags. Possibly this might be overkill for what it sounds like you have in mind, though.
Maybe instead a lightweight quilt could be worth considering - PHD do some very nice ones: