> 1. Find cheapest flights between two countries (country->city, city->country, country->country). Some people don't mind traveling a little just to reach the airport from where they can find cheaper flights.

You can sort of do this right now with comma-separated airports, like this: http://www.hipmunk.com/#!LHR,LGW.BOS,Next+Month.Next+2+Month...

The only restriction is that the airports must be in the same time zone and there's a cap on how many you can list for a single location (maybe 5?)