While thinking that Fallout was never meant to be a Real Time game, it got me thinking of a combat system in a game that successfully married real time elements with RPG: Parasite Eve.
To convert FOnline to Parasite Eve style combat would require that, when a player fires their weapon, all AP is consumed. What would follow would be an "evasion" period, where the player would try to dodge enemy fire or seek cover until the AP was recharged for another shot (the rate of the green bubbles recharging would be determined by both AG and the weapon's firing speed, converted from the former AP cost).
Also the targeting system could perhaps be improved, imagine if both the target and the person firing would stop momentarily when the trigger was pulled. With subtle differences like this, one could have more of the tactical situations of turn-based combat while speeding up duller positional activities (such as movement).
I don't know if any of this is possible within the coding, but I do think it would be interesting if players had another option for controlling game time other than the two choices available; especially since the same gangers who kill you with ten shots at once in real time instead die slow and tedious deaths in turn-based. There should be some kind of intermediate time to balance farming, PVP, and leveling needs.
With the "first shot, full AP drain" system, you would see less clicking orgies to get off five shots that would somehow screw up the other players five shots before their clicks can go through. Rather, you would see more of a smooth "click, recharge, click", with aspects more akin to a duel or a dogfight. Players would jockey for position, and the high AP player would still have an advantage in getting off more shots over time.
It might not be so easy to see, but departing from the model of "click-flurries" followed by a refractory period would surely result in a positive change for group combat. Since everyone is essentially "first shot spent" in the same way, players will be better able to adapt to changing battlefield positions (and even new combatants). Not only would it be more difficult to be killed by a first-shot volley (it would take slightly longer to pew), escaping players could not run as quickly from a group if they were targeted multiple times by the aforementioned "freeze frame" weapons effect.