Here’s a link for SD Express controller from Phison.
These comments still relate to older technologies, and may not apply to SD Express. (Though admittedly one initial appeal of the idea was the cost saving possibilities.)
If the newer SD technologies are indeed reliable enough, then the costs of implementing them may still be too high, because they are new technologies. And weighing in the chaos of having people buy unreliable cards does cause problems.
But still, the prospect seems like it still might be viable if these controllers and cards do indeed turn out to perform reliably, and the costs are not too high.
People would simply have to understand the risks they are taking by implementing such solutions, just as they would for the PC. Perhaps in this case, it would not be wise to include an ultra-convenient gui for such a thing unless the gui could also warn against the risks of using older SD technologies.
Even still, the interface could easily give warnings, and a readout of whether or not the SD card was an SD
Express or not.