As regards changes in Zeppy's personality, the whole point of the FC version of the man
was change. He started out one thing, ended up being another. Obviously it would be in the interests of the writers to make the two versions of FC ZC as different from each other as possible, so obviously at most one of them could be similar to the TOS ZC. And probably neither would, since once you establish change, you can bet that more change is in the offing.
But who would pick him up when he splashed down?
Why "splash" down? He could have parachuted right back to his Montana shacktown if he wished.
The American space program chose water landings and the associated hugely expensive recovery efforts because they were afraid of using retrorockets for slowing down the final impact. The space capsules could have landed on a desert with a combination of conventional parachutes and last-second fireworks, like Russian capsules did and still do. Or they could have been equipped with glide parachutes and landing skids, as briefly intended for the Gemini capsule. Cochrane would have had both technologies available, plus precision guidance and more maneuvering power.
Generally, Cochrane would want to be as self-sufficient as possible. And he'd probably wish to leave his warp engine in orbit, possibly with a scuttling charge attached, so that no competitor would get his greedy hands on it.
On a similar vein, the co-pilot seats on the missile could well have been for Lily plus one observer representing the financial backers. Cochrane would want to keep his space shot secret, but not so secret that nobody would believe he had exceeded lightspeed.
Once Cochrane learned of a nobler goal for his launch, he stopped worrying about the fact that Sloane was injured and the money man had become a smoking crater, and invited his new "astronaut" muses aboard instead.
Timo Saloniemi