The fanservice bits, as I said, don't really do enough to give an advantage over people who don't. The Amie thing does increase your support points a bit, but ultimately, making that person battle with another person like in the past Fire Emblem games is still more effective and faster than the Amie thing.
And while there are weapons that strip opponents, they have to have a WT advantage to do that and they are weak and alot of weapons easily surpass them in stats and effects. I've been trying to get a confirmation on what the hot springs do. I don't think they actually do anything stat-wise, but so far, I haven't found anything that says what they do besides fanservicy stuff .
So as far as I've checked, the fanservice stuff gives little to no real advantage over one who doesn't use them. And as far as I've checked out, there's little to no fanservice in the stories besides one scene with Camilla.