I have, on a rare occasion, too hastily gone from the arrival pre-immigration area to international transfer (+security), and once in the regular departures area (where you would have access to transiting lounges like normal), ask the transfer desk if I can reverse back through security, to the pre-immigration area (to see a friend in the pre-immigration area, who was arriving, but entering the country). I just said I wanted to enter the country for like 10 minutes to see a friend at the airport. This was back in 2016 and when KE+OZ were in one gigantic T1 (ignoring the T1 concourse A gates 200+ for a moment). I'm sure something similar is possible today.

You could potentially use that to just enter the country after you transfer and shower, although it is a bit of a back-and-forth.