Perhaps you missed this, KL46Z was merged to mbed. A user Mike ported KL46Z which currently supports only ARM GCC. He was using a makefile and startup files which were written for KL25Z, I am feeling rewarded that it helped to port another platfrom!
I tested my GPIO mbed application which I shared for freedom KL25Z ARM GCC, with same makefile (not much changed). I was able to run it, debug it. I am going to add ARM compiler support and review the code.
Stay tuned, more freedom platforms are cominG!