When I make my graf, I start the wort fermenting the day before adding the fresh cider. I started doing that a couple years ago when the cider had sorbate in it and I wanted to build up huge yeast numbers to overwhelm it. Not exactly what you're asking, but close.
Also, I have read posts where people who have not had the time or inclination to make a big enough starter, have instead started a lower gravity part-volume beer to build up yeast and added the remainder of the wort the following day. Kind of like doing a starter and adding wort later. My objection would be in the storage of the wort prior to adding it to the main batch. You'd have to be darn sure you keep that as close to sterile as possible.