I grew up in the 60's and 70's and this is the exact "combo dress" style my Barbie had. While I was fascinated by it (and the related concept with slim slacks and a tea-length or floor-length over skirt) I also couldn't help thinking as a kid, "What is this thing? Is it for parties? Going to church? Special days like Christmas?" I was confused even then as to what kind of occasion a garment like that would be worn. I like it, I just can't figure it out.
Go for it and let us know where you wear it and what the reaction is.
This is the style of dress I mentioned in my comments after the post about your Mom and the pics of her wearing her sewn items. However the one I mentioned had an overskirt that was less gathered than the one in the pattern above. It was long and straight but slightly gathered and it did not extend across the front of the body, only came partway around. iirc
This puts me in mind of a wedding dress I made that was a princess seam knee length dress with a full gathered detachable overskirt that was removed at the reception. I love the look.
Many years ago m MIL asked me to make her a tulle long skirt and a tropical print shell and wide-legged pants. It was wonderful and very sophisticated. Oh, do make the wiggle dress!
While I think the versatility of having the two pieces is great in concept, once sewn up, they might be too costumey looking. I love that look of full over slim, ala I Love Lucy and you could certainly carry it off but how practical would it really be?
If you do end up sewing it, I can't wait to see your fabric choices.
Your choice of silk tafetta for the skirt was fab. I wish I had access to the great fabrics that you have in NYC. I shop at a chain store and I'm lucky if they have silk anything. It is a shame that chain stores have such poor quality.