I'm not sure why a civ should be compelled to drop everything and declare war on a long time ally because they built a telescope. It likely wouldn't affect them one bit since they are doing their own thing, much less enough to backstab an ally. If I'm against you invading earth, that's another matter, which ought to be left up to the player. The idea is to have a sandbox mode where the player doesn't "lose" because another civ completed a "victory" condition so the player can better role play the game. This probably looks like a checkbox in options. In game, the player will continue to get the same notifications that other players are making progress on their projects and respect and fear will work the same way it does now except maybe it begins to affect you more if you have competing project ideas. I don't think shared victories are necessary, but it might be explored for the event you are allied for x number of turns and are pursuing the same projects. The game would continue until the player reached a victory condition, but the world would have to live with the AI projects. This game works very well as a sandbox, but currently I'm compelled to turn off victory conditions in order to play a game on a somewhat challenging difficulty and not have the game become a race or a puzzle.