What would make it stand out to the rest ?
Make it something non fantasy genre.
WW2 or AvP universe.
MMO-like.
* Player viewed from top (like traditional MMO).
* Player uses non guided targeting system, like in FPS (unlike in traditional MMO)
* Unlike in FPS, all gear and weapons are saved.
* Unlike in MMO and FPS, player must buy additional ammo/weapons from in-game merchants or find in "quest" areas that cannot be bought.
* Like in FPS, you lose weapon and ammo in its clip, but can be retained by picking up. Unlike everywhere, it is saved forever on server (ie if someone was killed in labyrinth or similar area, it can be recovered by someone else after some time.) It also can create automatic "dungeon" area (if in some cave players get killed repeatedly, it gets a lot of items).
*Unlike in MMO, number of weapons in entire world is limited (to prevent a large amount of "abandoned" weapons and encourage re-utilization).
*Only you weapon never get lost, is your knife/pistol!
MMOFPS
*Like a FPS.
*Has large amounts of players (hundreds).
*Has huge world (hundred of hectares!).
*It will not revolve around one point, it has many points!
*Players are free to travel anywhere (ie sniper can alpine-climb on tip of mountain or get request for drop-in, of course if they don't get blasted!).
*Players can play solo (like sniper above) or get work like one man behind front lines do spotting job for artillery (controlled by players) km's away.
For both cases, you must create a character and possible to make many!
On which platform would you like it to be ?
All of them!!!
What graphics style would you like it to be ? ( or non graphics for interactive text multiplayers )
Something non-cartoonish.
What would they story line be like ? What is the theme ?
For AvP: You are Marine/Predator/Alien/Corporate. You need to progress through areas, completing historic quests, for example...* You are marine. Your ship got blasted by Aliens/Pred/Corporates for some reason and crashed. You/Team need to get to safety point (where your progress saved @ res shrine)through wildlife/Aliens/Preds/Corps/whatever get in your way. If you get into territorial area, you get PvP killed by other race player.
* You are alien, some dorks built their outpost on top of you hive. Get there and wreak havoc!
* You are pred, you are short on skulls lately. Get some from aliens or humans by means of hunt!
For WW2: Complete objectives to help your area to get rid of all means of oppression and move scales to your side!
*You sent to sabotage some allied/axis facility. Alone or by team means, get in there and reduce it down to ashes!
*You need to intercept some aircraft, using fighter plane or AA guns to break it.*There is an secret cache heard to hold some 1st class weapons. Get some for yourself!
Would you add interesting mechanics, can you create your own mechanics ?
Some were mentioned above.
* Both MMO-like and FPSMMO can be combined (just a option to switch between modes).
How would you implement a payment option ?
F2P. Insignificant micro-transactions must prove useful. Whew... I may add more.