Indeed. Well, I propose head (helm/mask/hood/whatever), body (armor/dress), feet (boots/shoes), belt, hands (gloves/mittens/whatever), cape, two hands slots for weapon+shield/two weapons/two shields/one two-handed weapon; two rings, one amulet.
Besides, while you probably can't wear armor and dress at the same time, you still have your underwear, so one more slot for it (I'm not sure about MC, but if we'll ever create an opportunity for choice of MC sex, I guess female could use it). Or maybe two slots, for upper and lower parts, like in Otherworld.
In WM girls also can use things like manuals, magic spheres, strip poles and so on. So maybe one or several slots for manuals/books/tutorials as well? And some kind of slots for girl room? I don't think we should build and decorate every girl's room like in Alkion, but if you give her strip pole or huge magic sphere, she can't carry it all the time, isn't she?
Or we could just use several (maybe about 5?) "general" slots for anything that can't be equipped directly, including furniture, books and so on.
I looked at Alkion, it also has shoulderplates and leggings, but they seems like an overkill to me. It also has quick slots in belt, I guess you should put consumables into them for using during combat.
I'm not sure about magic/skills system we'll have eventually, but we might also use special slots for spell books or skill scrolls.