The retirement plan software that I've been exposed to over my career (ASC, Relius, Datair, FTW), do a decent job of creating an amortization schedule and setting up a loan. But they are not designed like bank loan software. So changes are incredibly clunky at best. It's also very difficult to get the TPA admin software and a recordkeeper's software to agree to $ with a single loan that never changes.
So, any refinance is very manual, fraught with probable errors and guaranteed to be a revenue loser to the TPA.