Thank you all for your very nice comments.
Here's how I made it:
I did go up a size in the sweatshirt from my usual size. I cut all the pieces apart, and measured to find the middle of the front, and cut that line. I opened up the sleeves and cut the cuffs off the sleeves with my rotary cutter. I also cut the crew neck off. I ended up leaving the lower waist "cuff" because I wanted it longer.
I decided to quilt a lining because I thought it would look and feel better than the sweatshirt itself (and easier to slide on over other tops/blouses)
I then cut lining material using each piece as a pattern. I pinned them together , did not baste (lazy me, but works fine) I admit that the lning fabric I used is some cream polished cotton leftover drapery lining (cheap me!) (or frugal! frugal is better!)
I had found a YouTube tute about these jackets and also the one here, so I started in the middle of the back piece, laid my strips out how I wanted them (you may notice the front sides are the same from the button edge to the side seam, but the back strips are random. Sleeves are as close as I could get to identical...was running low on matching strips by then.) Sewed the strips from middle out to each side on all the pieces per the tutes. (press each one and used sizing before sewing on the next strip.) Then cut off extra pieces of strips to the size of the sweatshirt/lining. I also rounded the square edges of the front neckline and bottom of the front. I decided to run binding along all inner seam sides of the quilt sandwich for a finished look. Then, starting with the shoulder seams, stitched the parts back together- sleeves next (pinning first), then the long seam of the body side to sleeve side (which is how the sweatshirt was originally put together.) I did pin that also.
Then sewed the fabric button loops in place, did the binding (like my quilt binding, which are by hand on the back --or the inner side, in this case.) I also made sure the seams were stitched open with the binding.
When I first made it I had it pressed very neatly with the seams open...looked so pretty! But after washing, they sort of cam together but i don't want to press it.
I sewed 2 strips together and made the covered buttons. (thought the 2 together would look "quilty")
And there it is!
Things I will do differently next time:
*Use 2 sizes larger sweatshirt, rather than one size larger. I wish it were larger. It shrank a bit when I washed it. Still very wearable, but not as loose as I wanted. Or use quilt batting. I may do that next time and forget the sweatshirt..
*NOT cut off the crew neck, and possibly will add a small Mandarin-type collar. This one has more of a sweetheart neckline and doesn't work with every blouse or top.
*pin pin pin! I wasn't happy with one of the sleeves and I took it out and redid it after wearing it once. It was 'off' a bit with the underarm seams.
This was a fun and relatively quick project and the precuts made it easy-peasey!