Well here's my take on it.
If the original poster is at a "mass oath ceremony" than it's really an absurd request, as you are handed a paper with the words on it and you can mumble, sing happy birthday or do whatever you want. NO ONE WILL NOTICE. So in effect he/she can modify their oath to what they want to say. If in fact it's an oath "on the spot" at their office that's different.
However that being said, the original poster, who states he/she believes in God, (not agnostic/athiest or whatever) but due to separation of state and church issues is contemplating changing the oath. So they want to make a political statement to make a point!? Really!? You believe in God but want to make a political statement about separation of state and church!? Especially in all likelihood their scenario is a "mass oath" - which would take care of any supposed "moral problems" they had.
But hey, stand by your convictions, roll the dice, request the change and see how that works out of you.
I think poster number two summed it up correctly. "I would worry about more important things"
Like... what about the requirement of defending the country, seems that might have more real reservations for people. I wonder how many people, possibly even the original poster, really want to defend the country, at the potential expense of their own life, and yet still mouth those words!?