Con, it's an interesting concept for a game, and kudos for coming up with something rather different.
Personally I'm not a fan of negative points for non-participation (especially as the group stage schedule is quite full-on)
And could you clarify a couple of the scoring rules please?
In particular you say "10 points each win" - if a striker scores 3 times is that 3 "wins" (and 30 points) or just 1 win as "$goals > 0"? If a
For midfielders, what consitutes "dominating" possession? (More than 50%?)
There is a few other things I'd be aware of - but I'll hang fire until you can clarify just how the scoring system works.