A good time ago, I published a "Better Strip Dress Sequence" add-on, as I was really pissed by the sub-optimal behaviour of the game.
This was in my beginnings with modding, so all I could do was hard-coding the actions :/

DKZZ2 soon posted a detailed explanation about how to do it properly, but I was busy with other things.
Recently, for the Spa at the Tiber Septim Hotel, I needed using his advice.

So now you have a FULLY GENERIC Disrobe/Stark Reality/Nudespell :)

It will work on any NPC whatever wearing, even if the stuff comes from a leveled list.
Another great advance is that it does not REMOVE the items, which would CTD in case of a Quest item: it just unequips them.
Sooner or later (depending on the AI schedules), the NPC will dress back.

The spell (Disrobe) is available at the most logical place: the Shrine of Sanguine ;)
However, you'll HAVE to complete the quest before it will be offered by one of the NPCs there.
Anyway, it WON'T work to achieve the quest, as this is checked by a specific script.

The script is documented, so you can remove more or less of the stuff.
Currently it keeps the shoes and weapons, and the rings and amulet.
It is also possible to give it a range... 1000 for example...

The add-on may ony conflict with anything heavily modding the Shrine of Sanguine, or changing the steps!