[Optional: Unlimited funds/weight]

In a creative game like this one it would be an own-goal to not include a skirmish/sandbox mode.
Balance and challenge are great in campaign and super important in academy.

But there are moments in life when all you want to see is a metal killing machine, only limited by the game engine, ripping apart a small fleet in hud-off mode.

Hurts noone to include a skirmish mode that is independent of the campaign. You could even use it to allow public testing of new hulls and modules before implementing them in academy or campaign. 

 

[No Multiplayer Please (Yet)]

I don't care about competitive MP all that much. Not to say not at all as it usually poisons community and realism but considering a coop mode wouldn't hurt anyone.
The game can stay as close to the real thing as possible but still allow you to share some amazing hours with friends.