But is IBM's practice as easily circumvented? If they are literally inserting nops, then that sounds like something a quick binary conversion could erase.
If you could then update the jump addresses (which are relative to IP) -- definitely possible programmatically, then yes. However, I don't believe you had the permission to alter the system software on an AS400.
Not to mention, if you have engineers capable of doing systems programming and re-imaging the system, you're not a target customer for an AS400 or the AS400 is used in such a function where it makes no business sense for you to allocate "real" engineering resources (who are working on your core product, not your accounting system) for this.
The AS400 was/is meant to be a turn key solution: IBM profesional services sets it up for you, after which you run SAP (or the like) on it. It also already came with DB2 and is fairly interesting by making the database the file system (decades before WinFS failed, Hans Reiser went to pursue other interests and btrfs is promising but still unstable).
