You may have some valid points there, but I disagree.
I believe the main reason for ranked being unpopular isn't the rating or the matchmaking. It's that many people simply don't like 4 vs 4 arenas and prefer 8 vs 8 objective based warzones. I personally don't play a lot of ranked PVP, but if there were solo ranked 8 vs 8 warzones? I'd play the hell out of that.
Would all-ranked PVP increase elitism and toxicity? Quite possibly. But if it improved the matchmaking and generated more competitive games I'd say it's worth a shot.
Regarding "matchmaking is hard": Well, yeah, but mediocre matchmaking is still better than no matchmaking at all. How many times have you entered a warzone and instantly thought "damn, this is going to be bad" or "yeah, we'll stomp them" simply by looking at names, expertise rating, HP bars and class composition? I think it wouldn't be too hard to implement a matchmaking system that could minimize the most glaring mismatches.
And I don't buy the "small playerbase" reasoning either. Even with only 16 people of the same faction queueing at the same time the most basic matchmaking algorithm could improve matchups over the current "meh, just toss 'em in randomly" implementation.
But it's a moot point with Bioware obviously not caring about PVP...
tl;dr: Good idea. Mediocre matchmaking > no matchmaking. Too bad we won't get it.