I think a lovely touch to the game (And a more realistic view on things) Would be fleet logistical support. Every fleet needs its oil tankers, ammunition ships and repair barges! When you upgrade your fleet cap, it takes a percentage away for 'fleet upkeep'. I think you should take this out alltogether, and make the player manualy do this. HAve him build tankers and ammunition ships and send them out in his fleets, or leave them stationed at planets as temporary 'repair stations'. I dont think making un-supported fleets run out of ammo, or fuel, is what should happen, more along the lines of:
A logistically supported fleet will gain advantages, especially over long distance fights. The logistical fleet will provide a home away from home.
A logistically unsupported fleet will be at a disadvantage, especially over long distance fights. Ammunition and fuel will be short stocked, which will lead to a 'rationing' of whatever the fleet has, which means less firepower output.
And in this, I think there will be a place for that tanker that was spotted in the vid 
And the spikey thing at 2:43, what the hell is it? Also, the before mentioned 'cylindar' at 1:24 and another mysterious object at 4:24... Hehe.
Cant wait for the expansion!