Of course there are some tricks to making this work quickly that i know so that whole thing including the artlantis rendering took less than 10 minutes.
In making the fill for the mullions, draw the shape in the floor plan window with an arc or spline and magic wand a wall to it that is the depth of the mullion. Make the wall have a fill. Explode the wall and you have a sinuous fill of equal width. Copy the fill into the complex profile window.
For the next profile - the glazing and muntin, return to the floor plan, undo the explosion and change the wall thickness to the glazing thickness. Explode this and copy the skinny fill into a new complex profile window for a glass profile that follows the mullion. Of course, this makes impossibly curved glass but who cares since it is a fantasy anyways. So if it need to be real, magic wand the spline in the floor plan with the magic wand set to fixed intervals for flat glazing segments that follow the shape.
Viola. The one from Twelfth Night, not the stringed instrument.
Dwight Atkinson