Yes, well, I generally don't count devices because lets face it, they don't need any development apart from hearing their voice and seeing their forms, which you'll see anyway.
And there are some other minor characters I might forget.
Still, since most of those are minor characters, the list of major characters -AKA those that
need development- still floats around the 20.
And then there is actual development in StrikerS that could just as well have been cut. Now this is the editor in me, but what did Vice's personal development, or heck, the character itself, add to the story? Cut away Vice's drama bits and it has no impact whatsoever on the story. I mean, I like the character, and I like the story, but if you had put me on the editors seat, Vice's backstory would have gone *snip snip* in favor of more important members of the cast.