The same thing that is valid for everyone attempting to make an MMO is valid to you:1st-
Make sure you understand the challenge it is to make an MMO, it requires x100 the amount of work and time a regular game requires. That means not just time, but money and patience as well. A big team is required since you are talking about a huge quantity of assets, terrain, items, and so on.2nd-
Make sure your team's leader is someone with not only a lot of experience in managing teams, but understands the scale and sheer amount of organization a big project requires.3rd-
I recommend starting off with a small team, organizing and making sure everything works fine with that small team for a while, and then, increase the size.4th-
You will have to completely reconfigure CE3's internal network and overall structure to suit your own network and connection to the external application (standalone server).5th-
Define goals, my advice is attempt to make a tech-demo without the online structure and attempt to find investors for it, fact is, without money such a huge project can't start. Besides the obvious bills for the website, distribution, you will have to spend a lot to maintain the machines that will hold the server - depending on the quality of the team who is making your server application.6th-
Extensively describe your work in an appropriate game document where you predict and explain every single aspect of the game. I recommend the following template: http://www.google.pt/url?sa=t&rct=j&q=g ... dQ&cad=rja
And I could go on for days showing you how hard it is to make an MMO. If however you need some guidance, I'm sure a lot of people in the forum will gladly help you, just take in consideration, that for the past years, no true indie mmo was released with success.
After you have the tech-demo done, if it does look good, feel free to contact me since my team work in creating MMO applications, and have been doing so for the past 7 years, without doubt, being top of the line.
Cheers mate, I hope you succeed and most of all, have fun.