(I work for Mozilla. Speaking unofficially.)
I don't have a good answer to that question. I guess the straightforward answer would be to make an account on the bug tracker and vote (it's under Details), but my impression is that votes usually don't carry much weight.
Oh, and for the reasons you gave, please don't post bug comments in support, unless you really do have additional information or perspective to contribute. (And "there's one more person who wants this, and I suspect many more" is not additional information.)
I know Mozilla has had various iterations of tools for collecting input, all of them ending up abandoned eventually. The current iteration is https://ideas.mozilla.org -- which, given that it's a fairly recent introduction, might actually be paid attention to. At least for a while. (Yeah, I'm cynical.)
A more effective but higher effort and noisier mechanism would be https://chat.mozilla.org where you could try to dig up the right channel and discuss it directly with people, but that seems like it's probably not appropriate for your example.
I'd really like a better mechanism for this. I think it's one of our bigger gaps, personally.
As to your specific request, it seems like right now the current answer to that need is about:profiles for full-on profiles, and container tabs for the lighter-weight, integrated within a single session mechanism. It may be that the latter has sucked energy out of improving the multiple profile support? (Multiple profiles have been supported forever and are unlikely to go away, but I agree that they're not getting much UX love.)
But I'm not involved in that area, nor do I know how Chrome's profile switcher works other than that people seem to like it. I'm happy with container tabs, myself, but I recognize that they fulfill a slightly different need.