I really don't think that would become an issue. All the jobs aside from BRD and WHM have very clear identities. I would even support a GEO (or something similar) job glamour for CNJ/WHM due to the recent changes to Aero and Stone - that is the only other case of a clear disconnect between class and job. This is about having whole job identities preserved instead of hacking two together. Every other job is very much in line with their own identities.
And it's not unlike SE to offer some things to just one or two jobs. In order to unlock instruments, you need to level BRD - no other job has even a similar equivalent and we don't see people asking for one. ACN remains the only multi-job class despite people wanting other jobs to split (once upon a time people were clamoring for GLA to split into DRK/PLD for example to echo Cecil).
I don't think I can be convinced this would ever be an issue.