I am not actually too down on universe, but I am concerned that mgm and sci-fi are trying to cash in on the series and are going to taint the spirit of the franchise (the use of the words 'mainstream', 'younger audiences', 'younger characters' and 'less tech' sound like selling out to me) as such, there will probably be a fourth series starting in 2011. So I think a discussion on what form that would take is in order.
SG-1 worked because it was set on contempory earth, which made it unique in space exploration sci-fi (i.e. same realm as star trek rather than x-files). Some of the writing in the early seasons was awful - what ever happened to the giant aliens in crystal skull - they were too powerful to be our allies, so we forgot about them, that would never happen in later seasons. The setting of Atlantis wasn't so good, it felt too much like any other sci-fi, but it was good writing that made it work. I fear universe will have a bad setting, and I hope the writing will hold it up. I think they should go back to earth for the fourth series.
My suggestion is a big departure from the sg-1/atlantis formula, but after 15 seasons of them the storylines need to revolve around things other than exploration and futile battles against all odds (they were great, but it's needs to change before it gets repetitive). People complain about how we are too strong now (beam weapons, asgard core, etc) so the only way to deal with this without rewriting the past is to accept it, and start dealing with problems other than goa'uld/ori levels of difficult enemies.
The lucian alliance could make a good enemy if handled properly (they would need a better structured leadership), and there is no reason for the stargate programme to be secret as earth is longer under constant peril. We could set up colonies on other planets, trade with other worlds, and make politics and social implications of the new galactic order a much larger part of the show. Stories could have a feel like 'ties that bind', with humans starting to take their (rightful?) place as the dominant species.
Like daniel said, the petty quarrels of your world will seem so small when compared to what is happening out there. This sentiment could be a springboard for satiring our problems (international and intercultural) on earth in much the same way as the goa'uld and ori were used to satire concepts of faith and abuse of religion. The jaffa nation could be used to satire the tenancy of traditionalism to limit social progression. I see the stars of the show being people like the president and head of the military - the decision makers rather than the front line people. Front line people would take more of a secondary role (think major lorne, dr fraiser, dr zelenka).
As this suggestion moves away from the exploration/big bad enemy formula that has made stargate so popular, people won't like it, but i do and that's all that counts.