At the moment I am watching the really bad management of the development of Wild West Online, a game based on an engine with a really bad reputation (partially due to it previously making bad games which many view as scams) and being run by developers with no skill in project management and customer relations (or they are being good scammers). Please don't end up like them.

My advice is to think big but start small. By all means say that it will be a Birthright MMO but don't get hopes up too high too early. Make the only targets that you announce be ones that are simple. For instance, your first objectives might be:
* terrain design and player movement
* player interaction with environment
* sword combat with a default enemy

Then you might want to add character attributes and adapt the interactions/combat around them. Then you might do XP and tasks/challenges. Then you might want to expand the enemies, more environment work, add weapons, add classes, add spells, etc etc. If you have a small team (or just yourself), build it up as you go. Don't try to design everything at once.

If you release "pre-alpha" builds as you go, remember that it is you who is designing the game, not the players. Yes, you need to listen to them, but you are the one who is having the final say.

Best of luck,

Sorontar
player and server admin for Minecraft from Alpha version