Changing the calendar in NGER constants, is there any impact?

For reasons I do not know, calendar type R was chosen as the NGER calendar when it was implemented and the calendar itself being changed to a July to June calendar (as apposed to the standard Jan to Dec calendar as delivered by JDE).

I now have a issue as JDE have hardcoded the new leasing module to use calendar type R and expecting it to still be the delivered Jan to Dec calendar months.  I therefore need to return calendar type R to the JDE delivered values so want to create a new calendar type for the NGER July to June calendar and change the constants to used this new calendar type (albeit the same calendar as type R was before). Are there any unsuspected traps/impacts/issues that will result from such a change?