I was reading about the proyect, and i found that there's not much people working on all the things that shall be done. For that reason, i present a proposal.
Many games had expansion packs. I belive that if the UFO team concentrate on the basis of the game (the actual techs, ufos, etc.) and a basic storyline, its possible to make a final game. But only a first part. This allows to concentrate efforts to make the second one, with many ideas exposed in this forum.
For example, there's topics about new personal armor. But, why make a 4 o 5 levels of armor for the first time? Why many class of UFOs when you can separate the game in campaings (each one, a expansion set).
More specific:
First part (Final version of 2.X)
THE PHALANX RESURECTION
The storyline could be the alien first invasion, and the humanity response. In fact, no alien force (considering a human attack force over another civilization) would launch an attack with occasional UFOs flying over the enemy cities. So, the first part is just like an "defense testing of human capacity". This pack could have for objective, the anihilation of the alien earth main base on Antartica (proposal).
The after 2.X version:
THE ANTARTICA AFTERMATH
In this pack, the aliens change the tactics. More UFOS, new class of them, new aliens... The story: A focus on drestroy PHALANX and the appears of XVI as a tool for do it. It could finish with the almost defeat of PHALANX and humanity
THE FINAL BATTLE
For this one, the PHALANX think tanks discover a vaccine for the XVI, allowing the humans to push back the alien menace. It's discovered the origins of the aliens, and the packs end with the defeat of the alien invasion in a mayor battle on Earth and ultimately at the Alien planet.
These packs could be chapters of the history, with the same geoscape, motor, etc. The differences are in the tech tree, and the storyline. May be a new interface mod.... I leave this proposal for discussion.