Well there are several ways to screw up while you snigger about it - don't try using wonnafyt again after you deslow the matron (to, say, prevent her from retaliating a fireball), because she'll be teleported behind the rock. The rock is still there because you only ever killed one dragonguard. So you'll have to kill another one and that can complicate things (this actually happened to me

)
Another thing is, under no circumstances should you kill one dragonguard, move to his spot and then cast wonnafyt (as you would with a lemisi-wheytwut combo) since the matron will teleport to the stairs and you're screwed.
Other than that, it's really silly.
EDIT: And it only just occured to me that you can go full silly and not kill any dragonguards - if you have endiswall. Wonnafyt's allready something you can't guarantee, but if you get both glyphs you can endiswall the piece of rock and then tell the matron that you want to fight. So 0 dragons fought, topside available with minimum fuss.