Here's how I manage pajama etiquette in Qsuites - 2 strategies:
1. board wearing a skirt (men could try a kilt) and once inside one's Qsuite, pull up the PJ bottoms, then ditch the skirt. Just like changing on the beach. Then tunnel under the purple blanket and change one's top under there.
2. less elegant and more cumbersome, bring PJs from a previous QR flight in handbaggage, change in the showers or restrooms in the lounge before boarding, and then save the new PJs (which will be offered shortly after one boards) for the next QR flight.