Just a bit of experience with community based team projects... I've seen many on other communities I've been (still am) a part of in the past, and most of them have failed... Whether they be made with Clickteam software, Gamemaker, 3d Gamestudio, or custom Visual Basic or C++ engines... They all had a few similarities in why they failed... (though some of the initial work was very impressive...)
I see you seem to have one of the most important parts done... Having a clear plan of the entire project. That way, there's a clear goal in mind for all team members...
Also, be sure to keep all members interested and make sure they feel like an important part of the project. Some valued their artists greatly over their programmers, Others ignored the musicians, who happened to be close friends with another member...
Next, is the inevitable something drastic went wrong and we'll have to rewrite, scrap, etc a good portion of our work... That's painful, even for a solo project (I usually just use the scrap work as an easter egg in something else...). But even then, it's tough to keep morale up in those situations... Again, a good solid game plan from the beginning helps, but in the case that it may happen, make sure everyone really is aware that it may happen.
And finally (at least, of the things that stand out to me...), Power in Simplicity. If it's your first project, you won't be able to make the next epic game. Not that it couldn't happen, but you'd be one of the lucky ones... Now, simplicity doesn't necessarily mean dumb the game down... no... Basically, you'll have to make cuts, and find out what you really need to make the game happen, vs what would be really awesome to have in the game... An overly complex project can lead to headaches when something goes wrong and you can't figure out why.
A good suggestion would be to work on a small project as a team to see how well you work together, then get started on a big project...
And as it's a Construct project... I'm curious as to whether we can get a community contest started to promote the release of Construct 1.0 once it's released... Prize? What better prize for an indie/hobbyist game maker than to have their project featured...
Just throwing that idea out there... It would be nice to see the power of the "little guys" and what we can do when we have the tools to turn our ideas into reality...