This is a very well thought out break down, which is rare on the forums these days. Floyd had an extensive resume with experience against all kinds of styles. I think he could find a way to pull it off against Cooney given what you've laid out. I disagree with you calling Cooney "slow". He wasn't some speed demon, but he had decent hand speed and mobility for a gangly 6'6 guy he wasn't some lumbering oaf. Cooney might manage to tag Floyd, but as you said, Floyd had to be hit numerous times with numerous knock downs to get taken out due to his tremendous heart & conditioning. I think if Patterson makes it past round 5 without getting badly hurt, he starts to pick Cooney apart. That gazelle Punch would definitely land on Cooney's Jay Lenoesque chin at some point and I have little confidence Cooney remains upright.
Patterson is the better technician, but Cooney just too strong. On a side note, did Patterson land at all on Liston?
It's been a long time since I've watch both fights. I know they were demolition jobs, just wondered, off the cuff, if Floyd managed to land at all before he got flattened.