RE: WorkOrder Script error - msdyn_/WorkOrder.Library.js
I think what happens is that if you customise the OOB form you may potentially lose what the original form from Microsoft was suppose to be if you customise it too much.
I had an experience where someone removed subgrids on the main product form which then broke some Microsoft functionality we wanted to use in the future. I had to load up a trial to find out what was on that form originally.
I personally would like to get Microsoft's opinion on this for "best practice". I can see that both ways could cause issue in future potentially especially now that Field Service is updating on a near regular bases.