Warren, there is much you write with which I agree. Also some factors which are not relevant.
Firstly that 5/16" thick blade. I agree with you that it is unnecessarily thick, but I have a good idea why it is so, and will remain so. Why 5/16"? Well, that is how thick infill planes, such as Spier, Mathieson and Norris, would use. The Stanley #4 1/2 was designed to compete with these infills, and it is not a big leap to understand the choice of 5/16" thickness for a line of premier hand planes.
Further, at the time of these first bench planes being constructed by LN, the consensus belief was that tear out was best controlled by either/both a tight mouth and a higher cutting angle. Infill planes used 47 degrees, and cutting angles around 50-55 were considered "high" (outside Australia, where 60 degrees would be better for the local hardwoods). The thicker blades were never for tear out, but for controlling chatter, and they continue to do this very well. But is is overkill. My LN planes - a #3 and a #4 1/2 Anniversary - came with A2 5/16" blades, but I use 1/8" PM-V11 in them.
So why does the 5/16" thick blades continue (with other modern makers as well)? Two reasons I can think of: one is that there is the perception by buyers that "thicker is better". The other is that a thinner blade will require some re-tooling by LN. Yes, the frog can be adjusted to close the mouth, but there is not a lot of adjustment length to do this.
The higher mass of the LN (compared with Stanley) is not significant if you are an amateur and use machines as well. "Lighter is better" is only a factor is using these planes for extended periods. For the average amateur, the extra mass is really quite handy .... I am not saying that more mass creates a better working plane - mass has no part to play here ... I am saying that more mass increases control when all one is doing is smoothing or jointing.
I think that criticisms over the chipbreaker are overdone. Yes, there may have been years of production of short chipbreakers, ones that do not close up for planing interlocked grain. However the part played by the chipbreaker really only became understood by most (myself included) from 2012. I still do not see LN-made videos offering advice about setting up a hand plane with the chipbreaker. Like you, I perceive that they view higher cutting angles - by way of higher angled frogs - to tame tear out. Everyone has copied the "Improved Chipbreaker", and there has not been any progress in its design. What I see missing is some curve to the body. These chipbreakers are too flat and, when tightened down, the leading edge can open up. The leading edge is 30 degrees, which is far too low for function. I add some bend to the body. I also add a curved leading edge of around 75-80 degrees.
I still do not like the Stanley-style of chipbreaker. They are too thin - too floppy - for my liking, and either open up at the leading edge, or creep forward when tightened down.
A2 steel is not my favourite, although it still performs very well. I would prefer O1 for the fine edge it can achieve. However O1 simply struggles to hold an edge in my local woods, and PM-V11 is the best compromise for quality of edge, both fineness of the grain and edge holding.
Regards from Perth
Derek