While I really liked the idea of Cheren becoming a Gym Leader, I think that they took an incredibly poor approach in making him into one. I know it's just my opinion, but I honestly found Cheren too impressive (during his final battle at Victory Road) to be reduced to the FIRST Gym Leader of all things.
I understand that they wanted to leave his starter ambiguous, but take a look at Blue. In Generation II, which took place three years after Generation I, Blue was the eighth Gym Leader of Kanto and he still had his old team, except they replaced his starter with an Arcanine. I personally feel that this is the way they should have handled Cheren, especially since BW2 takes place two years after BW, rather than one year or even a few months. That being said, they shouldn't have emphasized on him being "new," and I think it really would have worked out if they made him the last Gym Leader with his party from BW (minus his starter, of course).
As for the other Gym Leaders, I really liked Roxie and Marlon, but I also liked Lenora and the Striaton brothers too much to replace them. However, their absence actually makes sense given that you can't access the first few cities of BW until the end of BW2, so I guess it was fine to exclude them.
The order of the Gym Leaders never really bothered me except for Cheren, so I would've made Roxie first and Cheren last, then bump everyone else down by one spot.
