Don't get me wrong - Missions are certainly an asset...
But missions take time to develop properly - It takes time to build a good site with security - Who's gonna use the site when it works and looks like shit, but hey - At least you have a couple of missions in there... And one of them actually even has some potential - My buddy Dave liked it - He's 12, but cool eh!?!??
Seriously, if anything, it would likely just be a fad, and if you do implement something cool - A bigger and better site will likely just steal it anyways - Get the basics working first, smoothly - Then go for the gold.
Everyone's seen missions. People want a site with some functionality.... Otherwise, only people who actually know what they're doing will be on the site (if that) - That's right - all three of them... Two of them the designers... The other a friend... What's the fun in that? Who's learning?? No one. You've already failed your mission statement for the site. That's right, you heard correctly - YOUR FIRST AND MOST IMPORTANT MISSION SUCKS!
Get the bugs worked out - A good mission takes a lot of planning (if not even a completely separate server) that will allow the users to solve it anyway they can think of - Not just one way, pissing everyone off. If you begin with the missions, you'll eventually just 'wrap it up' due to lack of patience and you'll be left with a shitty base that you'll likely never even fix - Soon, your code will end up looking like spaghetti - That is, of course - Assuming that you don't give up before that point...
In other words - If you can't already build packages like phpBB and osCommerce on your own - You're wasting your time - You'll never finish it - And if you do, it'll be a piece of shit - BUT, *if* you can build programs like this, then you already know what I'm talking about and don't even need to hear it - It's obvious. You already know better. ANYTHING worth while, begins with a well designed structure.
Take your time - Do it right from the beginning - Do your research - Implement the ability for missions to be integrated (this is certainly, at least arguably, important), but focus on getting at least 60-70% of the rest of the site working properly first before you even touch a single line of code for the missions. You'll likely find a few volunteers to help you out on the way anyways...
You'll be happier in the end - And more importantly, your guests will turn into permanent members, not people who sign in once and never return because the 'site' itself had nothing to offer but those same boring missions you see on dozens of sites - Oh wait, that's right - THEY CAN'T SIGN IN! You didn't design that!
You need a gimmick, and missions aren't it - You need something new that no one has seen before - You NEED it designed properly so it works. That takes planning and time - Why not build the site in the mean time? Instead of re-inventing the wheel... Going in circles with no direction...
If you can build the missions, then you shouldn't have much of a problem with building the site - What's that take? A month or two before you have a fairly good base?? You'll likely rebuild or at least heavily modify it later, but AT LEAST it's a start.
Hell, it can be done a LOT quicker if you know what you're doing - So why not just do it. Build a mission or two on the side when you're bored, if you must. You'll need to be constantly making them anyways - But FOCUS on the site itself, don't lose that until it's finished. If you do it right the first time, you WON'T NEED to rebuild it.
Don't be another 'tried and wasted' project - There's already enough of them out there...
Sorry if this came off a little rude - I wrote it quick, on a shitty day. I'm sorry.
I just hope you get the idea I'm trying to portray.
And of course, as always... It's just my opinion...

I wish you luck either way.... And look forward to seeing what you develop...
