I agree a single player would be rather nice.
As in, play through your faverourite maps, custom maps and suchlike across the galaxy to rid the aliens/humans.
To begin with , I would only make it a human single player, but eventually make an alien one.
In each map there would be enemies, but also objectives to complete to get the f*** outta there, or kill those f***** b*******.
Humans
Part I
Retreat
Part II
Regroup
Part III
Retribution
The thing that'll take the longest is making all the millions of maps needed.
Maybe make drawings (for layouts and styles), thmes, notes and suchlike on maps you need made, then put them up-for-grabs onb the forums.
Each mapper makes a map, and itll be a huge collaborative effort.
OR, someone starts a map, lays down the foundation, caulks it, gets the fundamentals done, then passes it to another pklayer, who roughly puts in walkways, and obvious things. This ges handed round to more people and In the end we have a good map with little time spent from each player.
The only flaws I see in this is:
The huge range in mapping skill levels (metro Vs. Blockworld)
Co-operation
Motivation
However, If any of the big guns give their support for this, then It could happen.
However, this needs TONS more discussion and serious, realistic thinking.
ATM, Its not realistic to make 20 decent maps by yourself, splitting the workload increases motivation, but what If the next mapper decides to do something completely different.
If you can think up an effective storyline, ideas for maps, and basically the grand scheme of things, make a topic and Id be happy to contribute.
And because itsan open development, who says the singlwe player ever has to end?