To answer your big question though: While being able to make your own handle is a handy skill, I don't see why one shouldn't consider the stock handle in the decision since it's already part of the cost (unless you're buying JUST the axe head I guess). Hickory is also not as easily available to others as it is for you... while I could shape a handle out of local hardwoods, it wouldn't be as ideal as one made of good hickory. Honestly, I think GB makes some really good handles with a good shape, nice straight grain (from what I've seen), and use a coat of linseed instead of the usual varnish finish which makes for a nicer grip... I see no reason why I shouldn't consider that into my decision.
Actually, it goes a bit beyond this, IMO.
The OP was correct. Having a good head is the most important thing. But that does not mean that you would not necessarily put any handle length on a "good" head.
In general, a specific weight of head is good for a variation in handle length. As the handle gets longer, the head gets heavier. You can certainly vary the degree of handle length quite a bit. But, if you put a 26" handle on the 1 1/2 lb SFA head, I don't think you would be verry happy with it at all.
Another example, Kelly used to make a popular felling axe with a 7lb head, and a handle somewhere in the 34" range. I doubt you would want to be putting a 17" handle on that bugger.
The other end of the extreme is the GB mini. I really doubt you would like that head on a 24" handle

Just because it is a "good" head. You can only "fix" things to a certain degree, before you will be wanting a different axe head profile or weight.
I guess what I am saying is that with a good head you can vary the handle length to suit your taste. But, unless you are after some particularly different effect, there are going to be some limits to what you want to do.
Don't recommend it for car camping or as a back yard axe, but for hiking / backpacking, it's the best there is.
In terms of a "new" axe, I would agree with you. But, I don't believe it is the best there is. The reason is the "best" is subjective. What are
YOU going to do with it. For me, it is definitely not the best.
In terms of quality, it is still the best new one out there at the moment. But, in order to get my own personal "best" axe, I generally look to the old school vintage heads in the shape and weight I want, then match a handle size accordingly.
I was going to mention that reorienting the growth rings to perpendicular, rather than parallel with the edge can add a bit more power/ whip, but to take advantage of that may need a heavier head than what we are discussing.
I am certainly open to new concepts and would love to hear more about this one. But, it does however go against every published written work on axe handling/re-handling that I have ever seen. It also goes against my own personal experience with handle longevity. Do you have any experiences you can share? Type of tool, type of use, etc?
For those to whom this is a new concept, I will explain the rational for wanting vertical grain. In general, this is the direction that wood is going to handle an impact. When the axe face has force imparted on it, the force is put into the wood grain, instead of across it.
Think of the days when you played baseball with a wooded bat. You were always told to put the label up when hitting. That way, when the ball hit, it hit in exactly the manner it would on an axe with vertical grain. If you wanted a surefire way to crack or break your bat, you just turned the label towards the ball, and it was very easy to do.