How long do you plan on spending to work on this game? How much time are you willing to invest every day to get there? How many people do you plan on recruiting to help you out? How will they be compensated for their time and efforts? Do you have servers that will support 50,000 people? If not, how do you plan on acquiring them and will you have the money to continue maintaining those servers? Will you have people to provide administration/GMs for those servers? How will you compensate them? Have you already acquired a game engine that can support the amount of weapons and users that you are planning to support? If not, how much are you willing to spend on one? If you're planning on building the engine yourself, do you have a graphics engineer, network engineer, AI programmers, engine programmers, and how will you compensate them? How will you compensate the content creators? How will you compensate your quality assurance team if you decide to have one? If the game is similar to other games, will you be sure that your game will not infringe on intellectual property from those games? Do the human resources that you have already acquired have the time and money to invest in such a large project? No reason to stop dreaming, but the execution may need a little more research.