A long-term modification project for Homeworld2 that aims to "tell the story of HW1 in HW2" and simultaneously bring the game to a whole new level through a plethora of new content, graphical updates, overhauls of current systems and exclusive features.
This is one of the upcoming features for FX:Commanders. Yes, it indeed is what you think it is; you will be able to customize your own units in the future.
The translated screenshot is courtesy of QCD on RelicNews.
That is incredibly awesome.
Would it be customised before the ship is built and then set at that or can it be customised (read "refit") after it's built too?
That is something time will tell.
May I suggest you follow in Supreme Commander 2's footsteps, allow every aspect of the ship to be changed but make it so that low-level ships will still be able to put up a fight against higher-class vessels. In the second Supreme Commander (not Forged Alliance) you can lengthen gun barrels, add more gun barrels, upgrade engines for speed or power to increase refire rate, and so forth. But of course, you must do what you prefer, after all, limited creativity is not creativity at all.
Post suggestions at the forum -- they are more likely to be read there than anywhere else.