Lack of history is a big negative. However, 80,000 miles is not high mileage. I would be sure I had a PPI done that included compression and leak down tests so you know if it produces and holds compression. I would have it driven 50 miles or so and then check for codes. Valve stem seals fail enough that that should be a concern.

I place a lot of weight on the maintenance history so it might not be the right one for me but even if you take all precautions in the purchase decision sometimes you win and sometimes you lose. Because of that I would not recommend purchasing any 'old' vehicle, especially a BMW, because if you don't do your own repairs. If you DIY and it passes a good PPI it becomes what you already knew you wanted to do and how comfortable you are with the risks of keeping what you have or purchasing the 4.8. If you started this hoping for reasons to do this, do it. If you started it to hear why you shouldn't do this, don't.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas