I have done this while on a trip and my company asked me to be at another destination. It was cheaper to book a whole new trip rather than paying the change fees (plus more miles/MQMs for me ). I flew in, deplaned, waited for boarding to start and got back on. Was UG'd on both segments and FA instantly recognized me.

In this case they were distinct itineraries, each had its own BP and they posted without issue. Just keep your BPs as proof in case you need to prove you flew each segment.