I havent flown polaris yet but I often may want to change to fresh clothes. Especially on those annoying morning arrivals with no arrival lounge and no hotel to check into.

I just wear my socks in the lav and make sure to have a clean pair to change to. Plus if I have slippers I can stand on those. It may be a tight squeeze but its doable. I suppose a very large person may have issues.

I suppose PJ's is a different story. You run into the issue you speak of with not being able to change back into regular clothes. I'd say worst case, you could at least change your pants under your blanket without attracting too much attention. Then put on something over the shirt. Depending on how acrobatic you are, you can also change out of your inner PJ shirt once your outer shirt is on. That would at least get you through the airport and to your hotel without looking too strange.