The reason that "rules" was in quotes was because this thread was an attempt to asses if there was a view on what a "proper" end-to-end was.
A strange concept, perhaps, but it has elicited plenty of slightly different views which was the main aim.
My main feeling is that I would want to cycle all the miles in one trip (although doing it over several trips, even over several years, seems a valid approach).
A support vehicle is a blessing. I don't feel that having to organise all your own accommodation (perhaps on the fly) is a vital part of the trip; again some see this as the main challenge. This may depend on your cycling strength. If the main challenge is not to have to cycle an extra 10 miles at the end and start of the day and this is the interesting bit, then the legs can probably do it fairly easily.
If just making the pre-booked evening rest stop is going to be very hard work, then additional challenges are likely to be straws for the camel's back.
Possibly an unfair comparison, but is the main challenge real time accommodation selection, or is it just to stick with the bike rain and shine and get the darn thing to the other end of the country?
Some favour the Western side of the country because of the stunning views and perhaps some "real climbs".
Others such as myself favour the Eastern side of the country because it is flatter and after a certain point in the ride each day the main focus is on the next 50 yards of road hoping it is going to be kind to you. Views may turn out to be largely irrelevant for most of the day.
I am still mulling over the "two bikes" option (given a suitable support vehicle) with one geared and set up for extreme (for me) climbing and the other geared for longer flatter days. This changes the target from getting the darn bike end-to-end to getting me end-to-end with every mile covered on some form of bicycle. Tempting for me because although my N+1 isn't very large, I do select the bike for the weekly group ride based on weather and the proposed route. Again this is something of a luxury, but if I had some kind of major mechanical it would be nice to be able to signal the Team Car and swap bikes, and leave the support crew to get the broken remains to a bike shop for repair. Still smacks a bit of "I say, Jeeves, shall I ride the Titanium, the Carbon, the Aluminium, or the steel bed frame today?".
However possibly better than having to abandon because the bike developed a fault too major to fix quickly, as this is intended to be a "once in a lifetime" trip and not a yearly commitment. Also noting that if you are planning on doing 40-50 miles per day then bike shuttling logistics are a lot easier than if you are doing 100-150 miles a day when even the most dedicated driver is unlikely to want to drop a bike in for repair then drive a 400-600 mile round trip to pick it up again.
Conclusion; if I can get a support vehicle then I intend to use it to maximum advantage, probably including carrying at least one spare bike. Yes, my still being restored Dawes Galaxy might get a day or two of glory just because it can. If not I will either book all the way, or book in 2-3 day windows depending on legs and weather. No last minute B&B hunting however much fun it is.
Oh, and for an unsupported ride I will probably carry my emergency bivvy kit just in case I have to sleep in the wild due to unforeseen circumstances. Bus shelters can be your friend, I am told.