I presume that the backline structure won't change on turnover, the Brad ethic; expecting each bloke to man up in his position as stated on his jersey.
Kicking is the other issue - did I see an earlier suggestion that we could be thumping the leather off the Gilbert? IF so who is this kicker? I am presuming for now that Lucas is the bench utility.
I suspect everyone in the back line will be expected to defend in their position; this is actually one of the bigger factors behind my expectation that Stewart will be the main flyhalf rather than Lance. I do think we'll see Lance insert himself form fullback, Stewart's defence will really be a difference maker in the question of who starts at 10 but I expect both of them to be in the match day XV.
As for kicking in play it should be Stewartas the primary kicking option he's always had tones of time with the ball in hand and exploits any gaps in the defence; in the JWC and during the NRC last year even with teams using a rush defence specifically aimed at disrupting him, he had the composure of a 30 year old fly half, he'll be fine at Super most weeks.
Other options for kicking in play would be Lance, Paia'aua, Perese and I suspect Daugunu (but he scored virtually every time he touched the ball so we didn't get to see much of it). Also Tuttle in a pinch.
As for goal kicking I would say Jimmy Tuttle is likely to take the kicks he's proven to be very accurate over the last few years, but Daugunu is another 70% kicker, and Stewart can kick a goal or two (but hasn't in a while because he's been playing with other more gifted goal kickers (Godard, and Tuttle IIRC).
Finally regarding the JWC. While I would like to see Stewart get as much game time with the Reds as he can (and maybe even force his way into the Wallabies Squad as the only genuine flyhalf not named Foley).
I do think the U20's RWC can be a really important tool for the development of some of these players. I think Perese is a shining example of the impact it can have on a player.
Before the JWC Perese was very erratic and raw. Some examples include just running into blokes who are in the air, and not putting away players on otherwise spectacular kick chases.
When he came back from the JWC he was a changed player. Those little things that he wasn't quite doing right (because he was still a boy) suddenly because he got to do them in games against other boys -- he's nailing them. He's putting guys away on kick chases and not making those boneheaded plays. I think a little bit of responsibility and letting a young player be a superstar (like Perese is) really goes a long long way.
I don't think too many of the same things apply to Stewart, but I do think there are a few aspects of his game that he could really improve if he had a few games against easier opposition, like he would get at the JWC.