I think, arguably, the issue is, or perhaps always been, that this was intended by FDev to be a 10 year project. Not sure where that info is coming from but it seems to float around the boards, so let's assume thats correct. Braben et al clearly have their vision and presumably that is what they are working to. Players come up with a myriad of ideas in the community - some are just technically not possible, some might be technically possible but financially onerous to implement with little return for the effort, some are prone to exploit issues that are too numerous to address while the reality is that many are just not on FDev's gameplay and / or are not appealing enough to the player 'majority' to be worth it. It would be a waste of effort for FDev to implant 6 months worth of background effort to produce an arena that goes bust in 2 months of gameplay with only a 100 member usage, for example.
I think we do need to work on the face value of what FDev is telling us and what they seem to be heading towards, and while you can appreciate lots of people want to know what that is, it could be that FDev want to keep their plans under wraps, because a) they might not be able to do it in game, even if they really want to and try real hard and they would be publicly lambasted for disappointing or b) they don't want someone else cashing in on their idea before they get it ready with a parallel style game.
There is a suggestions thread on the forum, so maybe we just hit that with the ideas and presumably those that get the most positive replies should get some sort of response form FDev to at least provide some feasibility feedback rather than players feeling deafened by FDev not replying at all. Hard I know, but it does appear that FDev WANT community involvement and certainly the community appears to have been heard for a number of items but I think flaming and salt are an instant turn off to the FDev lurkers.