Real espionage - compromise enemy trade ships to gain vision, poison the crew of a capital ship making them lose a whole level of experience, blow up a trade port and frame it's government to drain loyalty of that planet, sabotage a gravity well to slow all production, steal research in the form of a cost/time decrease, and the cloaking stealth cruisers to carry out these jobs.

That might make for an interesting mod.  Give players of all races some sort of high level research that allows them to completely demolish a planet and remove it from the map (for a very large fee).  Maybe the mod could be called the "Vogon mod" after the Hitchhiker's Guide to the Galaxy.

"Your starting Terran has been completely eradicated from the game map so now you will die."

Needs a "random teams and go" button

Destroying a planet is way easier than most people make it out to be...

All you have to do is have a really big freaking explosion, and during that time, you change the mesh/texture of the planet to an asteroid field and then have a status that lasts for 99999999999 seconds saying that the planet is uncolonizable due to bombardment radiation.  Its not hard at all..

Also, new star types would be nice..  The following idea is reliant on this..

What would be interesting though would be if you could give stars abilities that affected all their planets so that different systems would behave differently..  Say you had a pulsar in one system so any interstellar bombardment would be mitigated some due to the incredibly strong magnetic field of the star.

What would also be interesting would be if you gave a race an incredibly powerful weapon that allowed you to use a unique form of starbase to turn a star into a weapon..  I'll just go down the list and what each race would be able to turn into a weapon..

TEC: They would gain access to a new starbase that would cause the traditional (yellow/blue/white/red) to create prominences and thus solar wind that could be directed at a target.  The result would be temporary orbital structure paralysis during which any ships and structures go offline for a few seconds.

Advent: They would gain access to modify neutron stars to turn them into pulsars that could then be directed at planets to cause the enemy to lost sight of their planet for a few seconds (due to radio blackout caused by the pulsar).

Vasari: They would be able to convert a black hole into a Quasar, which would then proceed to attack a planet, instantly wiping it of life and inhibiting colonization for 1200 seconds.  It also instills the planet with a permanent debuff that causes its population to be lower than it was originally.  The ability can only be activated once every 15 minutes and is incredibly expensive (both the facilities and you are paying per shot).

In general, I would like to see more researchables..  Perhaps more tiers for even more powerful ships for longer games.  But I definitely want more levels so that technological superiority can be accomplished and thus give you a real edge..