OK, good thinking, Chris. But I think the plan I've outlined isn't as weak as it might seem. (Whether it was actually what John had in mind we may never know.)
I think he could have brought the ransom note with him to the bank, shown it to the bank manager, and pleaded with him NOT to call the police, out of fear his daughter would be "beheaded." The manager would then be put in the position of being responsible for JonBenet's death if he called the police, so I think there'd have been a good chance he'd cooperate.
If the bank manager cooperated, then there'd have been no surveillance. This was of course risky, but the whole plan was a huge risk. He probably felt he had no choice but to take that risk.
No. He'd have collected the cash on the 26th. The "kidnappers" would have "monitored" him collecting the cash and thus called "early," as stated in the note. He'd have gone home, completed his staging, collected the body and all the other evidence, and waited till dark. If he were extra smart, he'd have made a copy of the note on his computer, so he could show it to the authorities later. But the note itself would have to be destroyed.
At this point only Patsy, Burke, a few friends and the bank manager would be aware of the "kidnapping" and all would have been sworn to secrecy. So the police would not be involved at this point. Then, under cover of darkness, he'd have driven his car to some remote spot with the body in the trunk, and either dumped it or buried it, depending on how comfortable he felt that he wouldn't be spotted. If anyone noticed his car in the area, he would have explained that by claiming he was delivering the ransom.
Well, we have no way of knowing what he was thinking. But I've thought it through pretty carefully and imo he might well have gotten away with it. I think it was an excellent plan. We should never underestimate John Ramsey.