I'm getting a custom Waltly gravel build. I'm going with a 12x142 thru axle, but in order to "future proof" the bike, I'm considering an interchangeable dropout. That adds 80 dollars to the cost of the build (but includes the extra dropout). I figure having the option to swap a 650B between an MTB and Gravel bike might be advantageous. So are there any disadvantages to an interchangeable dropout vs. having the dropout a solid part of the frame? I'm 66 inches and fluctuate between 145 and 160 pounds, just in case that matters for the conversation.

the interchangeable parts seem very well supported by the frame so I don't think there would be any disadvantages other than a bit of weight and $80.

Why stick with 12x142 though instead of just going with a 12x148 rear end?

Quote from: bxcc on September 09, 2020, 02:27:28 PM
Why stick with 12x142 though instead of just going with a 12x148 rear end?

Initially I will be using my current road wheelset, DT Swiss P1800, 12x142. I've got 700x30 tires on it (Schwalbe Pro One), just outside of DT's recommended tire width but it works well for my needs and abilities, right now mainly city riding, unfortunately. 

I'd go boost and just get a non-boost to boost adaptor. That way you future-proof your bike.