good Ideas. I'll just point out how we would do each one:
1, 2 - Game
3. myleague.com ... Sure we could make our own, but why spend the extra time on that when myleague.com has it for free. Making our own would be wasting time that could be put towards the v2 mod

...We could also link FOJ and the ranking page together.
4. find out how many people have a microphone. If enough people do, then we can use programs such as teamspeak or ventrilo (ventrilo is much easier to setup, and I have used both. It even has text chat for those that don't have a mic)
5. don't know anything about hamachi so can't reply to this one
6. Anyone not using the same nick are dq'ed. If you can't make your name inside Flatout 2, use this tutorial:
http://flatoutjoint.com/index.php?option=com_content&task=view&id=14&Itemid=327. Is there a way to view replay online? if there is, then if someone is purposely hit off the road, use FRAPS to record the part of the replay that they hit you off. Otherwise no arguing that someone did unless if you have video proof.
8. FRAPS. easy as pressing a single button.
What would we do if we have tourneys with custom cars?
1-2 are clear i think.
3. we go for myleauge.com?
4. there is already a TS server with a flatoutjoint cafe:-)
5. we keep that one open till we tryed normal hosting.
6. nick is not a issue, we use 1 nick for tourneys, and no changes alowed.
7. there is no replay thingy in FO2 so it looks like we must believe eachother?
8. fraps it will be.
First we try ingame cars, then it must be not to difficult to do custom cars if all use the same carpack.
I hope we getting somewhere now:-)
About making our own tourney, i gonna ask Marcellus once again, maybe he can be helpfull, because he had a dedicated site i think.
I think there is much time involved to keep a site like that running, so i can offer my help for that, hes dutch so we can understand eachoter:-)
Keep editing here, i see that Mottz has already a running tourney?
Maybe its not very handy to invent the wheel again?
I shall PM him.