Nothing wrong with carbon towers, i use both a front and rear on my b-max2 and none broke. Carbon is strong (enough) and light. It's not weird that some towers snap on the B-Max4 (knocks on wood), the tower is much easier to hit and thus brake.
I still run the 3MM since i haven't broken it. I know people who run the 4MM and they haven't broken anything.
I don't think that the B-Max2 will be discontinued soon, it's a different platform. But I think that the B-Max2 had some serious development the last year (and a half) and the car is 'done' (at least for a while now). So parts will still be available (some parts with the YZ2 are interchangeable), that's no problem. Lots of tracks in EU/JP are indeed high traction, in the US it's still a lot of... well, very low grip tracks.
I'm also curious about the shocks, I like the current (with the new shock bottoms) shocks very much though.