Horsetail clearly prefers sun, in my yard, so I don't know how it would do inside. Really annoying noxious weed. I hate it. But I agree it is actually quite attractive! I think you might as well try. I would not worry too much about the invasive bit-If it is growing in your neighboring ditches, wouldn't zillions of spores already be wafting throughout your property? For strong vertical mass in bathroom, I think snakeplant is useful, I have a bunch of varieties, some more vertical than others. They are slow growers, so you might want to buy a sizable one.
