Your computer already supports that. It's called "swap".

The M10 are over produced and only PCI-E 3.0 2x lane devices but 16GB of DDR5 is going to cost over $200.

You can do the same with USB-C M.2 adapters but the adapters cost more and eww USB for Swap, hope the device never drops.

In any case DDR3 isn’t nearly as bad price-wise and would have much better energy efficiency than stacking 1–2 gig sticks.

For starters, The slowest sticks of DDR(x) are often slower than DDR(x-1). The issue is never capacity, but rather, performance.

The real nonsense? USB? It's a mess. Pick a USB cable and buy it from ANY retailer, let's make it easier, buy a USB-C cable. What is the data rate (depends on cable quality and length), Does it support power delivery? If so, how many watts? (~5W requires a very different cable from ~230W), how do you know from simply looking at the cable? If you buy a cable, how can you tell what it supports by simply looking at the connector? Imagine having a box full of USB-C cables. Could you tell me how fast each of those cables are? (The cables themselves don't! Many don't have any markngs at all, and if they do, the markings could be fraudulent)

RAM does not have that issue. A stick fits or it doesn't. Sure, there are a huge range of speeds, however, that range has a ballpark (JEDEC defines the ballpark, the "cartels" make the memory and push out some faster stuff).

While there are definite exceptions (I was bitten by one recently), you can generally plug in a DDR5 DIMM and expect it to work in the system.

The same cannot be said for USB. Some USB cables ONLY deliver power. Some only work with certain devices. I've USB-C (!!!) cables that only work with the devices they are shipped with, and even more annoyingly, the both may be true! ASUS (!!!) ships MOTHERBOARDS that can only pair with vital hardware via very specific USB-C cables (Strix Hive) and "GLORIOUS" ain't so glorious. Their mouses warn you not to use other USB-C cables, and they are right, depending on the make/model/generation, you can brick your "glorious" peripheral.

No, USB nonsense needs to stay far away from anything else.

Also, the reason this is a huge issue is because the memory makers are cartels. Only a few of them exist, they gang up and bully EVERYONE and nobody has ever invested money to create a competitor due to this, except China, which of course means that the U.S. and portions of the E.U. are insta-banning/trying to insta-ban, even though it is really freaking hard to install spyware on a memory module.