That's good news about the 2.5" SSD flash drives. From what I'd read to date it seemed like the better ones were using decent (random read/write performance oriented) algorithms, but the cheaper ones were still using a fairly naive approach (and, eg, getting much slower as soon as all the flash cells had been written at least once). Perhaps we're further along the "adopt the IO controller" curve this time than I thought.
As you say, the (physically) smaller devices (CF/SD/etc), especially at the low cost end of the market, are always going to be constrained by available processing resources. So maybe some sort of "direct media control" API is the most optimal answer at the low end, especially if we can avoid the worst of the "fakeraid" situation (one-OS-version-only binary blobs). (There's also a higher risk of bricking the drive if you're moving, eg, a SD card back and forth between something doing its own low level access and something using the higher level API and firmware access. But like the NTFS driver presumably eventually enough the details will be right that people can trust it. And embedded devices with, eg, internal SD, can mostly ignore that risk.)