A tough request comparing a harem anime with a specific character-type like Charlotte. But I'll try my best to remember one anime that I watch that has a character similar to her, but the main lead actually falling for her is what makes it tough.
Yes I have, I've been watching all the recent animes, so if you are curious about any of them do ask Infinite Stratos does have a harem setup. It also just proceeds with it, there is "some" plot in Infinite Stratos, although I use that term slightly. The majority of it is about fan-service and girl-snatching.