Originally Posted by
Ditto
I'm not accessing it while transiting, I am accessing it after I got it off the belt at my final destination and before heading out of customs.
And by then your carry-on will have been checked (at least in theory) or will be checked if you can't show that you've been on a itinerary with a transit at a Schengen airport before arriving at your final destination, which is a Schengen airport as well.
Originally Posted by
Ditto
[Snip] then he can take one packet through customs for me, there is nothing illegal about it.
It can still be illegal. Once you bring in goods that are not for you personal (or for your immediate family), the limits do not apply to these goods. Obviously, it's impossible for a customs officer to proof, that passenger bringing in smokes doesn't smoke.
Originally Posted by
Ditto
But again, this bathroom transaction can take place before entering Schengen in the same way it can take place before leaving the destination airport,
No, because anyone in the non-Schengen area will be liable to be checked by customs. Unless you are just slightly over the limit, there's no way past customs (at least in theory).
And please just stop. I've linked you the rules. Those are applicable regarding when and where your checked baggage/carry-on has to be checked by customs (at least in theory).