You have to dismount and swap side to keep same rotation direction on the Contis. This will help if your camber is a little off and you are getting a little higher tread wear on sides. A little more air pressure can help with this as well. If the tires are wearing even all the way across the tread, don't worry about it.
Also, all modern light passenger and truck tires have synthetic rubber. About 50-60 percent. Without it, they would be HORRIBLE in the rain as natural rubber is very hard and doesn't provide as good of grip. Race tires have higher composition natural rubber.
A can o fix a flat would me a smart option. If you are concerned about TPMS issues, get an actual M mobility kit. Basically their version of fix a flat along with an air pump that plugs into your 12v. I would imagine BMW would warranty any TPMS issue if their kit was used, but you should inquire with them first.