Nobody cares how much liquids you have when you clear emigration, that check is only performed at the security checkpoint, which you point out is at the gate.

The Servisair lounge in non-Schengen was recently completely refurbished at AMS (http://www.executivelounges.com/loun...nge-terminal-3).

Since security is at the gate, you'd really have to manage missing your flight. I doubt they'll close the gate if they still see someone being processed by security.