Regarding what Satoshi expected Bitcoin to be: no one should care.
In my opinion, he is an outstanding genius but nobody is smart enough to understand the best use of Bitcoin in the future.
That is true. One should not choose between small-blocks or big-blocks just because "Satoshi said so".
However, looking at
why bitcoin was created helps understand why it has certain features, what consequences they are expected to have, and whether it is a good idea to change them.
Would it be a good idea to modify a car so that it floats, in order to get a vehicle that travels on water? Obviously not: because every detail of the car's design, from the four rubber wheels to the placement of the license plate, was determined by its original goal of traveling on roads. Those details are totally wrong for the goal of traveling on water. If you want a vehicle for that purpose, you should design one from scratch,
starting from that goal and letting it guide all choices along the way. The result will be totally different, of course: a boat instead of a car. Even if your goal is a vehicle that can travel on both roads and water, the result will not be at all like a car.
And you had better justify why you are designing a new boat, rather than buying an existing one. Just because a new car is better than all existing cars, it does not follow that adapting it to float on water will yield something that is better than all existing boats.
In this case, reading Satoshi's writings can help us see and understand bitcoin's limitations and capabilities.
It cannot scale enough to replace VISA, and it will make a lousy medium for large settlements, because it was not designed with those goals in mind. If we understand the reasoning that led to certain details of the design (like the 1 MB limit and the abrupt halvings of the reward) we have a better chance of predicting what would happen if we changed them.
Those who want to reform bitcoin so that it replaces VISA or ACH should put bitcoin aside and start the design such a system from scratch, choosing at each step the gears and rivets that are better suited to those goals. But, first, they should justify why the world needs a better option for those goals and why they think that they can design one.
(That said: in fact, I believe that, as a software engineer, Satoshi, was much better than Gavin and Mike, who are much better than all the Blockstream developers -- who are totally incompetent and irresponsible in that regard.)
The only mechanism able to make Bitcoin fullfil its potentialities is the market. The market is a mechanism of agregation of knowledge and no human being can outsmart it, the market is collective intelligence at play.
1 000 000 average people are more knowlegeable than one outstanding genius. 1 000 000 people are more knowledgeable than 20 decently intelligent Blockstream employees.
So you think that 1 000 000 traders could have designed bitcoin?
The market is only the average of all the trader hunches. For a purely speculative asset like bitcoin, the hunches cannot contain any intelligence, and the average is still a random value. The bitcoin market is like a headless pig flying in circles, chasing its own tail. (Hm, wait, I think I must work some more on that metaphor.)