http://www.reddit.co...n_tf2c_lobbies/
I've played countless NA lobbies using the E2TFL configs and had the opposing demoman using the loch n load or the engineer using the short circuit, both weapons banned in UGC configs. Several people seem to think it's because of laziness sometimes, and other times it's because the player wants to use weapons banned in UGC. You can't stop the second reason, but not changing the config to the league correct to the region because you forgot to click the right drop down or w/e can be fixed by making the default config used locked to what region you're in (UGC for NA/SA, E2TFL for Europe, etc.)
tl;dr Default config should be based on what region you're in, not just E2TFL for everyone because banned weapons kill NA lobbies.