Remake a new coat out of old down coat filling?

I have a 30 year old Eddie Bauer super long down coat that has seen its better days.  Now there are too many rips, tears, patches, and worn areas to keep the down in for another 30 years.  But there's lots of down, and Eddie Bauer down is the cleanest I've ever experienced (no smells).

So, not sure what to do with the old coat yet, I bought a brand new down coat from another good manufacturer for a good price in after season sales.  Unfortunately, I started sneezing up the wazoo when I put it on for 10 minutes after I got home to model it to my husband.  Something was wrong with the down, in my opinion (not cleaned enough?), and so I sadly had to return it.  I have a down vest, another down jacket, and a down comforter I sleep under every night.  All fine.  Alas, I'm getting off topic.

So, I want to save this down out of this old coat, and perhaps sew a new shorter coat and fill it with this really good Eddie Bauer down. Has anyone ever done such a thing?  I have no clue if this is even reasonable, but I'd hate to see this down be left to sit idly in a coat shell that just isn't practical anymore to wear.

Of course it's reasonable! People have been making down coats for a long time :D  
It's not complex, basically just a puff quilt. There are patterns online for those, and I suspect for down fill coats too.  
I want to see pics when you do it!  :D

Any chance of adding a presentable shell on the outside?

I recall that feathers/down require an incredibly tight weave fabric (ticking) to contain the pokey ends. That could be a challenge in repurposing the down.

(Then again, what do I know? I use square knots when sewing on buttons. )

(Then again, what do I know? I use square knots when sewing on buttons. )

said Douglas Alpenstock. . .
Nothing at all wrong with a square knot and a button - it makes a better job than all those shoddy efforts produced by lazy manufacturers!