Ah, yes. I might have mentioned GV. I was on GV, too, but switched my carrier from Verizon to Google's Project Fi a few months ago. I have to say, since that switch, my experience has been great, and all of "this stuff" we're talking about works much better (e.g. SMS, MMS, group text messages just work like you expect, with not caveats or aggravation, or having to explain to Mom that I have three different phone numbers...).
I'm just purely speculating here... but I wonder if at least part of the reason that some of "this stuff" hasn't been solved is that Google has been focused on making Project Fi work?? Maybe that's why GV still doesn't integrate well, etc.? I would have to guess that their stack of development priorities is really complicated and intertwined, with all of these various initiatives going on.