Hello,
CO11N is operation level confirmation and CO15 is order header level.
In case you want to do fast entry at operation level CO1V transaction is available.
In case you still want only one confirmation at operation level, then assign a mile stone confirmation control key to your last operation and confirm only last operation using CO11N.
You can read below for more details on mile stone confirmations:
Milestone Confirmation - Production Orders (PP-SFC) - SAP Library
This will not be a radical change, may be you need some update in routings if you decide to switch to a milestone confirmation control key mass update tcodes CA85N and CEWB are available in standard SAP.
Hope this helps 
Best Regards,
Ameya B.