Doesn't help that the Switch's ROM cart is actually slower than the Nintendo 64's.

SSD's are flashed based memory.

Just like RAM, you have two options.

Faster memory chips or more memory chips in order to leverage memory transaction parallelism.

The Switch is also CPU limited which is why the CPU boost-mode can assist in reducing load times rather significantly, loading isn't always about the storage side of the equation.

You have Radeon image sharpening.
In the Xbox's regard, they support DirectML which is the Direct X variant of DLSS, I expect Vulkan/OpenGL to roll out a similar feature at some point, enabling it on the Playstation.

So they have similar capabilities.

Running games direct from the current carts isn't ever going to get much faster is it? Gonna have to buy digital or hope for an 'install to disk' option to see load times disappear?

Switch 2 is going to be possible as a home console long before it can be a hybrid. That's fortunate for Nintendo because the only way a home console could beat the (not actually a) hybrid is GPU power, QoL improvements and exclusive games.

Cartridge speed can be way, way, way faster if Nintendo wants it to be. 

Nintendo is not ditching the hybrid concept any time soon, not a chance. The sales speak loudly. 

There are ways to make a hybrid console more powerful discreetly anyway. 

They're limited by the carts not the card reader, no? They could make new carts but I don't see that happening.

I'm not saying they'll ditch the hybrid, I'm just pointing out what it takes to beat a hybrid. Even handhelds can't compete so it will take a lot for a home console to beat hybrid sales.

Nintendo could use PCI-e 4.0 express lanes if they really want for a cartridge solution, that would make the cartridge blazing fast. There are new hyper-fast SD Cards that are doing that, Nintendo could likely do something similar for their cartridge slot if they really wanted to. Ironically this is probably something Nintendo of the 90s would prefer. It wasn't really a big deal last gen because many devs are still running games off a Blu-Ray disc at the time and the Switch was faster than that, not much point in going overboard. 

I'm talking about improvements I want for the current Switch.

If I had a choice between a combo, I'd choose a Switch 1 hybrid and a Switch 2 home console (2-3 years earlier than a hybrid successor) over a Switch 1+2 hybrid 2-3 years later.

That's never going to happen, Nintendo is never making another "big box home console" ever again. 

Maaaaaaybe they'll do a micro-console with no screen eventually as a minor release, but that will be years after the proper hybrid form factor. The hybrid form factor is the sweet spot for Nintendo, they're never going back to non-portables as a major part of their business ever again I don't think.

The best you might get is maybe a "premium" higher end Switch SKU that is more like a mini-laptop that folds out and can really stretch its legs in terms of power. 

The hybrid can still come 2-3 years later and swallow up the dedicated home console sales.

The portability is the star of the show, Nintendo's had really a miserable better part of 25 years now trying to sell a home-only console, it just doesn't work for well for them. When you make a a home only console people expect things like a modern online infrastructure, all the modern 3rd party titles, or you need a miracle craze like Wii Sports/Fit were. 

It's just too hard for Nintendo to manage that, the hybrid concept gives them the differentiator from the PS/XBox brands they need while integrating the market strength of portables which quite frankly has been their stronger side for decades now. 

If Nintendo wants to do something more along the lines of what you're suggesting, maybe a premium high end Switch that it more akin to a mini lap top could work. That could have a higher end chip and then in a couple of years the chip could be die shrunk to fit a more normal size handheld I guess.