This might be of interest to some: As I mentioned earlier in this thread, I have a flight through HEL today with a long (almost 4 hour) layover. I thus decided to try and leave the Schengen area to enter the lounge in the non-Schengen area, and this worked without any troubles whatsoever. Less than ten minutes after landing I am now in the aforementioned lounge, having used automated passport control (where you don't interact with anybody who might want to see your boarding pass). Only slight downside is that I have been told that as my flight leaves at rushour, I would be advised to leave the lounge about 45 minutes before gate closure - but given the length of my layover, I can live with that. Anybody else in a similar situation might want to give this a go.