1) Its improbably, but not impossible. I mean last game had a freaking ESRB review video as it's big leak..
2) No it doesn't, there's enough reason to believe that Richter was started before Simon seeing as 90% of Simon's moveset was also used by Richter, exclusively Richter in a lot of cases. He's also more popular than Simon in Japan. It could easily have been that Simon was decided on to join the roster using the moveset designed for Richter but label Richter as the Echo Fighter due to Simon having seniority.
3) If they wanted to include a 5th Generation Pokémon as an Echo and had to have them based on a Pokémon (we don't know if Echoes can be from different series yet) and they decided to include Gardevoir, Gothitelle would be the best choice since none of the others in Gen 5 align well with any other Pokémon on the roster. Also, Sakurai lucked out with Greninja, he didn't know if he'd be popular when he chose it.
Fact is, it's not disproven without a shadow of a doubt yet, it's still feasible if unlikely.
Remember that people also tried to shoot down the ESRB leak as 'obviously fake' because they thought Shulk was a photoshopped Little Mac and misaligned lines.