Could you have security inside a lounge?
 

Could an airline have a lounge where half of it is airside, the other half outside, with a security point in the middle? It seems like that would get a lot of frequent travelers to join the lounge, to avoid the regular lines, and also never have to see the terminal/checkin. They could also have check-in and bag check there too. Seems like it would be a lot more civilized. I'm sure there must be something prohibiting this though.

Lounges would have to be moved. Airlines wouldn't pay for it (they don't even like paying for cardstock), and most airports aren't structurally suited for it. You'd have to knock down walls, build new enclosures, etc.

Funny you should bring this up. Just this year JAL installed such lounges at Tokyo Haneda Airport (Tokyo's domestic airport). There are special lounges for Diamond and JGC Premier members (those who fly above 70,000 miles in a year) that have their own security checkpoints inside the lounge. Personally, I don't think there's much need for this at Haneda, as the security lines are usually not long at all.

The Mapleleaf Lounge that was in the old Terminal 1 at YYZ had this arrangement. You entered the lounge, then were screened.

Isn't this also the case in the new F terminal at FRA?