I think the issue with less variety in the various Maslany incarnations is indeed a natural progression since one would expect that by this point, the show would have probably introduced most of
the clones already. So the plot shifts now to delving deeper into each of their personalities and individual storylines, which I think the show does very well. I like how we know that it's the same actress playing each of these roles, yet each has their own distinct personality and characteristics thanks to the way the show is written and the way Maslany brings it to life. So in terms of variety, I think the source is not through more incarnations, but the development of the existing incarnations.
I have to disagree with Gavaris being sidelined though.
In fact, I catch myself wondering more and more in S2 if he is more than meets the eye or really just Felix in the way that Sarah knows him. The reason is because he seems to be the only person outside of the clones that is aware of what is happening and actively involved in each of their lives.
He's constantly there for Alison's domestic problems and acts as sort of her advisor, he is of course always there for Sarah, he's there when one of them needs something to be done (e.g. - transporting Helena to Art's place), he personally acquired and setup all of their new green mobile phones, and though he's involved with Cosima to a lesser degree than the others he also interacts with her, not to mention the fact that his apartment has doubled as their own "home base" or something to that effect So I definitely don't think that Gavrais has taken a step back this season. If anything, he's become a more major player in the show.