well my first item in the wish list is

To make a patch so I can start the game on "my" PC
Bots
definatley more female characters (since I am one)
more space levels
more brightness ( I think some levels are just too dark )
less lag

Dream sequence -

What really DID happen on board that space station that you escaped from?  Why are you such a legend amongst other Marines?  Perhaps it would be possible to include a flashback level at the beginning of the next expansion pack if it features Matthew Kane, and then you could wake up aboard the Hannibal ready to undertake your next mission?

Persistent corpses -

While I understand that Raven are using much the same method to guarantee good framerates in Quake 4 as ID did in Doom 3 by clearing dead Strogg from the level, it just doesn't have the same effect as walking round and seeing corpses littering the battlefield in Quake II.  

Plus there's the inconsistency that there are Strogg corpses in the Medlabs aboard the Hannibal, but I never once saw one stay for more than a few seconds after I killed it.

With this change Raven could also reintroduce the Strogg Medic unit to the game, and have the repair drones you see in parts of the game sneaking round and resurrecting dead enemies.

If not that, why not have a boss enemy with attendant repair drones or medics that you have to take out to avoid them repairing it?

Enemies -

1. It would be great to see a Strogg combat unit that could grab its human victims, drive a spike into the base of their skulls and implant a neurocyte there.  

These hapless victims would then be programmed to find their own way back to the Stroggification plant to be modified further, or used to lure their fellow marines into traps (perhaps lying wounded and calling for a medic like that scene in Screamers?)

2. Enemies designed to use psychological warfare.  What about Strogg units with fully aware, limbless torsos of Marines attatched to them, with loudspeakers attached to amplify the
Marine's horrific screams of agony as they are electrocuted?  

3.  The Strogg Voss Prototype Boss would make a really good intermediate enemy in any stage where you are in a vehicle, because at the moment there seems to be too little graduation between cannon fodder and huge battle machines.

Traps -

Quake II was littered with traps and secrets, while Quake 4 has hardly any.  It was traps and secrets - not to mention the inventory system, which Q4 lacks - that gave QII much of its personality.  

When you think about it, the Strogg would have much to gain by using traps because these would be a great way to harvest bodies to make further Strogg from, without expending ammunition or troops.  

Any traps from the history of warfare (especially those used in the Veitnam war) could be taken and given the Strogg touch - just the right mix of high tech and simplicity.