Twilight 2000 4th edition combat
I run a T2k 4e game here on RPOL and I think that the key is for the GM to do all of the dice rolls based on player declared actions. We're gradually working out how best to do declared player actions as we go along, but it has become apparent that, as well as declaring Fast and Slow actions, players also need to declare the number of Ammo dice they are using on an attack, what stance they are in, whether they are using things like NVGs etc and whether they will push a check or not.
I also generally ignore initiative and instead work on the principle of posting a GM turn post and then asking each PC to post their turn posts when they can - if you ask players to wait to post until their initiative point comes up then you're going to wait for a long time and make the game even slower. I think that this is the approach on most games on RPOL though.
I should also point out that I use the optional combat rules to use a 2m grid on a map rather than 10m hexes, though I doubt that this makes a significant difference on RPOL.
This approach works well and means that I end up with a list of actions for each PC and NPC. I then make all the dice rolls for each action, work out how the narrative of the scene flows and then write it up as my latest GM turn post.
Does that help?