I pointed out the idea of play-by-post as a way to get his fix, and he had questions about how one could run combat effectively without turning the game into a grind. I'm going to address these with fourth edition in mind.
Ways a DM can make play-by-post combat fun and exciting:
- The DM rolls all the dice. It tends to speed things up for players at the expense of DM time, IMO.
- Ditch the strict initiative. I tell the players that their character goes when the player posts. That allows the player to fit his post in when his time allows it.
- Give the players a time-limit on when they can get their posts in. You don't want to be waiting for players to post. Make the time-limit 1 or 2 days, tops (and consider a weekend to be 1 day). If they haven't posted by the time-limit, too bad, they lost their turn.
- Play up the narrative. When you post, don't just hits and damage. Make sure to write up the narrative-side, make it exciting. Make the players shine.
- Structure the combat encounters so that it introduces new complications with each (or nearly each) round.
- Dialogue. Have the villains talk during combat. Mix the "role" and "roll". My favorite example is the conversation between Luke and Vader during Empire Strikes back.
- Provide alternate win conditions instead of just beating all monsters to zero hit points.
- If you find the combat is going clearly in favor of the players, and they are in the "clean up phase" where they are simply hacking at monsters until they're dead, call the fight. Ditch the dice and write up a flavorful narrative on how the players clean up those last few goblins.