Tires: Tire replacement, united arab emirates, emergency maneuver

Question
Hello there,
I'm guessing you get this all the time, but would help to have your advice on my current situation.

I own a 2008 G35 infiniti. I live in Dubai, United Arab Emirates (Middle east). I have a tread mileage of 15,000 kms. I have noticed off late that one of the rear tires (passenger side rear wheel) is always dipping in pressure.
The tires on the back are 245 45 R18 95W.
I wanted to know:
1. If it is okay that i change just 1 tire of the same specs given the little kms run.
2. If I were to change the make on the rear tires, is it okay to have two different manufacturers. The one i have on right now are Bridgestone Potenza.
The car and tire dealership i spoke to here say that these tires are not stocked and advice a long delivery time for them to come. So I were of the opinion to go for a set of new tires in the back or maybe wait a little longer and get just one of the same make.
I also dont want to replace only two tires at once. But given my present situation, i fear this tire manufacturer has lost a bit of a confidence in me.
Hope you understand my problem and I await your expertise advice on this.

Answer
John,

Cars tend to pivot around any odd tire in emergency maneuvers - and the more odd the tire, the more the tendency.  Since it is fairly rare to need to do an emergency maneuver, think of this as a risk.

To minimize this risk, replacing a tire with exactly the same tire, except for wear would be the second best option.  Obviously the best option is replace all 4.

Replacing the tire with a different brand increases the risk - Not to mention, that if this tire is placed on a drive position, the drivetrain is going to suffer some additional stress and wear - and, of course, the longer it is on there the greater the stress and wear, which may ultimately lead to a drivetrain failure - low risk, but it's there.

So the answer depends on how much of a risk you are willing to take.