It's your job to post your dreams and our job to kill them.
Sadly, an all-too-accurate assessment of many of the replies to this and similar topics -- but kudos to those who also chipped in useful advice!
Yes, making an online game is a difficult undertaking. Yes, an MMO is beyond the capabilities of the majority of would-be game creators.
But here we have an original poster who doesn't want to make a WoW killer, clone EVE Online, or make the next RuneScape. Here we have someone who wants to make a simpler 2d game. That only wants to support a maximum of 5,000 players. That isn't interested in being a global success, but just wants a game people in his own country might enjoy. A person who apparently at least took the time to create some sort of design document, and appears to be trying to do their due diligence before recruiting a team.
Is this still difficult? You bet it is -- it's a difficult undertaking that would entail a lengthy learning and development process, and probably a couple of smaller (perhaps failed) games along the way.
Is it impossible. No, it's not. Single developers and small teams have succeeded at more difficult projects than this one.
Here we have a user who specifically noted that this would be a "super hard" project and wants to do "whatever it takes" to succeed. Someone who specifically asked not to be warned about the difficulty, claiming to already know; it's pretty obvious from the mention of this that this is someone who has done some basic research and seen similar warnings before, and although probably underestimates the difficulty has chosen to continue anyway.
Some of the most impressive projects around come from people who stubbornly forge ahead when faced with difficult or "impossible" challenges. When community member Danny Green started with his goal of making high quality professional games by himself many people considered it overly difficult or not impossible until he started to show impressive progress. Danny now has two impressive games released: Urban Empires and Gettysburg: Armored Warfare. Flavien Brebion worked by himself for a good few years before building enough of a following to attract help he considered reliable enough, and his goal of a space-based MMO set in a highly detailed procedural universe seemed like an overly difficult dream. He still has a long way to go, but Infinity has progressed in leaps and bounds and is incredibly impressive. It's been around a decade since Radu Privantu created his small scale MORPG Eternal Lands -- and while it's no WoW or EverQuest it has attracted a stable and sizeable player-base.
Obviously these successes are the exception rather than the rule, but for the rest of us schmucks attempted and failing at these types of project is one of the absolute best learning experiences available. When you tell the original poster that (s)he is underestimating the difficulty of this project what experience are you basing that on? In many cases it's based on your own prior attempts at an overly ambitious project in which you would have learned a great many lessons and gained invaluable experience; I understand the drive to try to prevent others from wasting their time, but why rob a determined beginner of that incredibly valuable learning experience?
Warning someone about the difficulty is fine -- perhaps even a good idea if they seem unaware of what they're getting into. But when someone claims to understand the difficulty -- even if they're probably underestimating it -- why continue to push the point? Sure, give the advice if you feel it's necessary, but how about some actual detailed ideas for how to proceed with the project as well? Maybe the original poster is one of those rare driven people who will just keep at it until the project succeeds, or maybe they'll fail and learn all those lessons more experienced developers harp on about. Either way, post after post telling them their project is "too difficult" or "impossible" just isn't helpful.