I would push for a new car as well, or at the very least make them loan you an x5 that is the same spec as the one in service.
I told my SA I would drive the X3 loaner for two weeks max then I expect an e70 X5. They have one more week before the X5, it will be very intresting to see what they do if my car is not ready.

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"It's a family thing"
2007 e70 X5 4.8- Wife's
2003 e39 M5- Mine
1995 e36 M3- Track Car
2004 e46 M3- Mom's
2006 e60 M5- Dad's