Browser based can work.
If Deadly Games was rereleased browser-based I'd probably be all over it. That's a perfect example of how these mechanics can lend themselves well to being browser based.
Then again, I think the whole game can function browser-based pretty well. Simple graphics, depth elsewhere.
I also remember multiplayer not being much fun in DG. I'd love to see multiplayer work like so:
1) The ranks of MERC being built up heavily (and likely randomized.) You're now bidding with other people for mercenaries. You can hire for X missions, or make offers for mercs currently under contract for when the contract ends.
2) Missions also being bid-based. There's some scouting info, a difficulty rating, an intel quality rating (intel isn't always accurate), etc. People bid for the missions. Winner is the person with the best rep, lowest offer, and perhaps some form of guarantee. Makes you really balance how much you want to spend and whether missions are worthwhile.
The issue with #2 is people want instant action, not lengthy bid processes. So maybe the bids can be high prestige missions, yet there are plenty of instant-launch missions waiting as well, for set amounts of cash and prestige. Maybe you need to do the bid missions to unlock certain things, like membership into better guilds, etc.