Tire incident

Wife went over a little border (the kind in the middle of the road to separate lanes going in different directions) and damaged the rear right tire.
I could complain a lot but she also managed to change the tire by herself on a car she barely knows (new to us since the 10th June) ... hopefully once back home, i will not discover some other damage.

Now comes the question of what to do?
I doubt that I can get the tire repaired so sounds like a new set of tires.
In this part of the world, I think I would go for the Michelin XM2 but at $130+ a pop I'm wondering if I could get away with changing 2, keep 2 of the originals on the car and one in the garage just in case.
Would that be ok or affect handling and fuel economy badly ?
If ok, would the new ones be better in front or rear or I shouldn't care because they will be rotated at some point anyway ?

 

Actually checking the currently mounted BF250 Eco tyres, i'm starting to wonder if i should just get 4 XM2. The BF250 Eco are not particularly good tyres in terms of rolling resistance from what I can tell but more importantly if I understand the numbering correctly, those have been manufactured the 24th week of 2009.
Although they don't show any worrying sign, isn't 6 years old a bit old for tyres ?

 

Got 2 Michelin XM2 mounted on front and thinking I'll change the back in a few months.

Thanks for all your advices !

 

A bit more than little for sure but what damaged the tyre was the broken and sharp edge i think ...
That also pinched the side skirt a bit ... nothing too bad but still.

I guess the good side of the story is that with the two XM2, wife likes the handling better and has already asked if those side skirts could be replaced by something "less plain looking"