Best bet is to do the job preimposed and eliminate the booklet workflow from the driver.
So for instance.
Print the PDF from Acrobat and use Acrobats Booklet function.
So in the driver Paper > Other Paper Size > Advanced Paper Size
Match these settings
OK > OK, Now set Acrobat to do the booklet imposition itself for the BW portion of the job
Then go back in the driver and do the Inserts of the color pages. Document Options > Special Pages > Covers
In this driver trays are not chooseable, so I used "Type" as an example
Lastly the fold and staple and trim, Finishing > Booklet Creation (See the icon lower left to the right of ?, click that to get the right side window) The key is the Preimposed by App this tells the driver to fold and staple but not rearrange/resize pages
Note the screenshots are from a 560 with Freeflow, but any freeflow should be the same or very similar and I believe your D125 is Freeflow.
I have a b/w D125 printer with finisher and trimmer and a 570 color printer
I have to print a 32 pages pdf on my xerox D125 b/w printer. Page size is 8,85 X 12,6 in. and I need to create a booklet, fold and stamp. I use for this booklet SRA3 paper (17,7 X 12,6 in).
The problem is that pages 1,2,31,32 and 15,16,17,18 are colored. This means - the first and last SRA3 page from my booklet. I have printed this pages on my 570 color printer and I put them on tray 5 (bypass) of the bw printer. I want the printer to take only the first and last page from tray 5 and for the rest to use blank paper from tray 3.
Note: cannot use tray 8 (inserter) because the maximum supported size is exceeded.
Someboby suggested me to use the copy funcition with build job enabled.