Demar DeRozan IMO is an obvious choice to be bumped to the second unit this year. It may not start out that way but should be looked at. Considering Calderon's familiarity with Derozan already and the need for a scoring punch/1st option on offense in the reserves Derozan would fit that role to a T.
Starting would be a pretty solid defensive line-up of
Pg - Lowry
Sg - Ross
Sf - Fields
Pf - Bargnani
Pg - Calderon
Sg - Derozan
Sf - Kleiza
Pf - Davis
C - Johnson
One thing you notice about the second unit is Calderon has played with all of them so there is not much chemistry building required. Derozan becomes the #1 option of the second unit (he will also play with starters at times in games) and plays with players who he is familiar with. If he starts he is adjusting to Lowry while still remaining the 2nd or 3rd option. Calderon will be a grand facilitator playing with Amir,Derozan, & Kleiza. If you switch Ross to the second unit he becomes their best scorer as well (arguably Kleiza on some nights) but is still a rookie that you're relying on to be #1 option on the floor. If Ross can start and play good D he will still remain in the flow of offense but will not have the pressure of leading the charge. Bargnani, Lowry, and Fields can and will score. You could argue that Ross would have to get used to Lowry as well, same with Fields and Bargs, however Bargnani isn't as dependent on his pg for his offense and Fields is in the same situation regardless and doesn't require the ball as much or for it to be hand wrapped for him like Derozan.
Casey needs to make Derozan realize it is a tactical move and not a demotion, it is not to say Ross is a better player. It simply gives the Raptors a two headed monster. Line-up A & B if you will.
Many line-ups are going to be tried but for a team without a "superstar" the depth of the raptors is what will keep us in games and I feel Derozan if accepting can carve out a role as our go to scoring punch off the bench. A younger, stronger, more athletic Barbosa playing for his job with more leash to play for it.