Mistress Kamillah uses cartridge pleating on the skirts of her gamurras (you mentioned sleeves, but the skirts are where it really pops), and hers are the best I've seen out there, re-creation-wise in SCA-land. These are contemporaneous with your gown's time, so I think cartridge pleats are a viable solution, lacking absolute proof. (To me, "viable" is everything -- if you can make a reasoned argument and provide encapsulating evidence where absolute proof is scant, then you're doin' yer job to the best of anyone's ability.)

Can't wait to see your Ken Doll wearing it!