Aside from the fact that teenage(-and-younger) girls give gifts of clothes to each other and expect the recipient to wear them as matters of tact, I don't think that your greatest tragedy is entirely true. It is unlikely that the implications went completely undiscussed at the Frederator tables.
I really do agree with Seibert and Muto on this though. Adventure Time peeks in the dangerous realm of young-adult storytelling. Where a brand misstep can completely kill a series, or worse. Nick might be willing to hazard more whole-family oriented material, especially with the success of Avatar, but Frederator's work doesn't really comport itself to the general audience expectations for something with themes or not-quite-subtexts more erotic than, "Hero gets kiss from girl."
Maybe an Adventure Time feature of some kind could take those kind of risks and I can't do anything but trust that Frederator knows how to pick its creative battles with Nick.