Adapting a boardgame to a Online Multiplayer Game

Today I did a bit of research about porting boardgames to online multiplayer games

A standard, turn-based game has a clear set of rules. When porting it for example to PC, some decisions have to be made, and if the game is going to be multiplayer, those decisions become critical.

The game mechanics can get to one of this states:

• Keep the pure, turn-based rounds. The most obvious one. This means having to wait for the CPU to compute it's turn (which as of today is instant except in games like chess ;). Example: Magic The Gathering.
• Keep turn-based rounds, but with time limit. Each player has a time limit to make his decisions. If time expires, turn goes to the next player. This is good to create a "pressure" state in the players, but generally I don't like it. Example: Space Hulk boardgame.
• Switch to real-time. This may appear trivial to do, but very often a game is meticulously designed to take advantage of careful turn planning, so switching to real time may crash the game experience. Example: World of Warcraft.
• Develop a mixed-mode. This is the approach I'll probably choose. Action takes place in real time, but each action has a cooldown time, so you have to plan what are you doing ("are you going to slash into the skeleton skull with your sword, which is fast, or are you going to throw him a fireball, which takes 3 seconds to cast?"). Example: Final Fantasy VII's Active Time Battle.

Another option that I don't see suitable for my game idea is the Conditional Turn Based system, in which there are no rounds, but a "timeline" of turns that gets modified by each player and/or NPC actions. It is similar to the Active Time Battle, but more reminiscent of turn based games (and I'm searching for a way for the game to be more real-time, not more turn-based).

So... What would you choose? Would you play like in D&D in pure turns? or you would prefer a more real-time like experience?