The overwhelming consensus is that it is not just not a bad thing but actually a good thing to re-visit and re-use a pattern already made. (I thought so too.)
I finished cutting out the jacket and skirt last night and the biggest left-over bit of my 2m of fabric is about 35 x 45 cm (maybe 1 sq.ft.). I sure hope I didn't make any mistakes!
I am going to insert black piping at the curved line formed by the pocket edge and front waistband seams, just for fun and because the detail of this line is really rather beautiful but would completely disappear if I didn't do something to make it pop in my dark and textured fabric. To unite the two pieces, I'll continue the piping at the CF, collar and lapel edges in the jacket. Or maybe at the horizontal seam...
Here, as a reminder, are the line drawings:
Where do you think piping would best be inserted?