I'm not saying he's impersonating Zephram Cochrane. I'm saying that Zephram Cochrane's role in the invention of warp drive appears to have been grossly exaggerated... BY ZEPHRAM COCHRANE. And if you go by First Contact, it would appear that the Enterprise crew were the ones who originally gave him the idea to take all the credit himself. It's a self-fulfilling prophecy: Cochrane goes on to claim that he alone developed the warp drive engine and bask in the spotlight as history retcons the facts and identifies him as a great man. Why? Because he has been told by the Enterprise crew that history says he alone developed the warp drive and is a great man. Since clearly nobody's going to care about the facts anyway, he might as well take the credit.What else do we need? Everybody around Cochrane seems to credit him with the invention. Nobody expresses a contrary sentiment, not even Lily Sloane. And that ought to rule out the idea that the ST:FC "Cochrane" is some random guy who stepped in the boots of the real Cochrane who looked like Glenn Corbett.
When did Lily get a chance to set the record straight on this issue? The entire time on the Enterprise Picard mentions Cochrane's role in history only once, when he says "Actually we're not unlike yourself and Doctor Cochrane," to which Lily quietly snickers. She doesn't get to sit through any of the gushing about what a great man Cochrane is and doesn't get the chance to say "Zephram? He's just a janitor. Mike Ocuda The Third invented the actual drive."
Only (apparently) in the 24th century. Those caps are never canonically identified in TOS, nor is the grillework on the front of the TMP vessels identified as having any similar function. The Excelsior and Oberth classes do not have ANY identifiable features there.They're a must-have for the Federation style of warp, though.
And to weigh in on the antimatter issue, I can only AGAIN point out that the script for FC explicitly described the Phoenix's warp drive as being powered by plutonium salvaged from a nuclear warhead. Data's line about Cochrane converting a WMD into an instrument of peace makes sense ONLY in that context, since an ICBM by itself is not actually a weapon.