I'm not sure if this has been suggested yet, and my apologies if this is a duplicate thread...
But what if the sniper is a new character that hasn't been introduced yet? Out with the old, in with the new. Taking out Gambino (and the Von Helsons) would put whoever he/she is in the perfect situation to take over as the most powerful person on Gaia, don't you think?
There's a map missing somewhere towards Aekea, too. On one of the intermission-y type maps there's a path that leads up to nowhere, so perhaps somebody has a mansion, or there's a new town...