"Something that should be apparent to you regarding the riders on your list is that they all were able to ride around problems EXCEPT one glaring name"
Hate to say it, but that's not necessarily true of Sheene.
"How big of a difference in your estimation is the bike he is riding now to the bike he crashed 3 times with this year?"
Well, a different chassis is a fairly significant change and I would bet your left testicle on the fact that they completely revised the mapping before the deadline on changes to electronics. As Colin recently opined, you're only as fast as your head allows and given the emphasis upon performance psychology, change a master cylinder cover or switch a valve cap and it could slash three tenths off these guys lap times. Which leads quite nicely to...
"Tweak his bike ever so slightly and he chucks it down the road."
Easy for us to say from the comfort of a recliner when all you have to juggle is a beer in one hand and the remote in the other. "ever so slightly" - How do you know? It has gone down in racing legend that on occasions Lawson used to intentionally lose the front in order to enter a corner quicker but because he was 'Steady Eddie' no one noticed. Imagine a rider like Schwantz trying it and you have Marquez. I've never, in forty years of watching this sport seen a rider employ such a high risk riding style. As much as it is a strength, it is his achilles heel and often a liability for those he races with.
"It was then and it is still now the best bike on the grid."
No it wasn't. In terms of what? Given your comprehensive and appreciable understanding of the dynamics of this sport and the associated variables involved you should know better than to employ such simplistic absolutes.
Incidentally, I hope you're prioritising our trip to Upton Park today. Biggest bogey ground in our history. Cemented into guidestones, the very lore of this sport that we never win there. If ever the time was ripe.