Basically I agree with the Romanians. Carlisle's coven will never be safe from the Volturi. Anyhow, no one is really safe; that Aro guy is like nuts, and any time you're around him he has about a 50% chance of saying, "You misspelled Carlisle" or something and you're history.
So what can be done? One good thing would be to catch Jane and Eric away from home. Say when Aro sends them in a month or two to wipe out the Canadian coven for revenge (it's a little too risky to wipe out the Forks group), could Alice foresee it? Carlisle's family could make a little road trip (with Jacob and maybe a few friends) and catch them with just a few other Volturi guards. As long as Bella's around to block their special powers, it wouldn't be that hard to destroy them. (If Felix comes too, it's harder. I would enlist Kate - if she can grab him and shock him, maybe Emmett and a few others could finish him off. Not easy.)
Getting rid of Jane, Eric, and maybe Felix would by itself pretty much put Volturi out of their position of power.
Now what about really getting rid of them completely? I think for that we'd need to take Aro's claim seriously: He said that humanity has developed weapons that could destroy them. Bullets can't do it, but how about a nice armor-piercing cannon shell - maybe that could cut a vampire in pieces? Of course, human beings could never hit them, but a vampire could. I'm picturing a raid on a military base, hopefully at super-speed without anyone noticing; we don't want it in the news. Then drop some really big bombs on Volturi castle. Better not to use nukes, but they have conventional ones that can destroy a city block. Take a plane or helicopter or two, drop a few of these bombs on the castle followed by some napalm to burn the pieces. Then Edward goes around the perimeter to sense if there are any still alive in the rubble, the rest of them pull them out and destroy them. Maybe?
Truth is that I don't really like most vampires. I'm with Jacob; even the "good guys" in Breaking Dawn are a bunch of murdering blood-suckers. Imagine if the world were run by serial killers... Once the Volturi are out of the way, maybe Carlisle could make an announcement that all vampires are becoming vegetarian from now on or being destroyed. (It would be unfair, I think, to make the law retroactive.) His coven can go around making spot checks on the other covens, with Edward to read their minds. No cheating allowed...