Disclaimer: I'm not saying that ambulance aircraft were never used in WW I (with or without red crosses) but it's unlikely simply because there were so few suitable planes for the purpose. Certainly, service type aircraft coulda been used on occasion to move casualties one or perhaps two at a time, but a/c dedicated to the purpose would be a novelty. And why would they be operating over the lines? Makes no sense.
I hope that Tony F did tart up HG's white D.VII. Modelers rejoice!
