Jon Vöge declares a hostile takeover:
Now, how you best maintain multiple copies/variants of the same Semantic Model is a whole other discussion but as a one-off, I was asked to merge the Measures of the two models.
Initially, the question actually stumped me as my usual tool of choice for external manipulation of semantic models Tabular Editor does not have a great native way to solve this.
Jon lists a variety of options and then gets the job done with ALM Toolkit.