Right, I'm not giving official approval here yet or anything like that, but in theory it's an Idea I'd put my name behind.
On an IC level, as best as I can tell, I'd say that someone like yourself and whomever else is willing to work on creating the tasks should do so. If HoHs are willing to help out, that's great, but if they're not don't force anyone, else they just don't have the heart for it. If you in particular want to play a role in this (Which I suspect you do) create a temp. character who can act as the Head of Games Department for the MoM, providing an IC outlet for you to play a part in running the competition.
If characters drop out for reasons of activity, sub in other ones (as we've done in the past.) Even if it is a bit of an IC hitch, it's better to have 4 participants in each challenge, rather than have the number dwindle and drop with each event, until only one competitor is left for the final event. Maybe, if possible, have subs for each team.
Judges should be fine, they can change with each event should activity become an issue (as was the case canonically with Crouch being filled in for by Percy at the Yule ball)
As for planning, as I've said in my email, it's of the utmost importance that you have everything planned out to a T before the event starts, now is the time to start planning. In the past we've generally done the first task, waited several months while we tried to figure out the second one, in which time site interest plummets, then struggled to find the motivation ourselves to run something which no one really gives a rats about. With that comes a timeline as well, have everything planned out (task wise, the Yule Ball not so much) well in advance.
And just on a note of personal opinion, a month of waiting might be a bit long, depending on how motivated and interested everyone is (going off the oct./nov. - first task, dec./jan. - yule ball etc.) Especially considering that not everyone in the site would be involved. Perhaps shorten it to oct. being the first task, nov. being the yule ball, dec. being the second and so on. That's just a matter of logistics though, and I'm not sure that either suggestion is 100% right so it'd be up to you.
But on a side note, I'd love to see this run almost entirely by a non-admin team, as I love to see the members take things into their own hands. That's not to say we wouldn't be involved or anything, and that we wouldn't help out, but having a majority member input on an event like this is exactly the sort of thing I'd push for.
Now lemme talk to the others before I say I support it going ahead