i think making The Last Stand - Union City with online multiplayer with other people will be cool,like putting party and stuff like that if you guys think its a bad idea then i guess so but it would be very cool if they did have it.
Its a little late for such a major upgrade to an already released game. Ask the developer and see if he can include it in the next release in the series.
You could just ask the creator to create one especially for online multiplaying. Remember, only the best of the best can create good quality 'live' games.
One of the main problems is that doing such a huge project like this costs a huge amount of money; this means you may have to pay him some or all of it if you really want him to post this game. For such a great game like The Last Stand, it may cost quite a lot of money but hopefully you will get lucky. Go to the creaters page now and request it! If he asks for money, just send him some although it is only best to give him any money at all, no matter how much it is, if you are at the age of around 18 or over or if you have strong permission from your parents/guardians.