In 2012, at the Akademy (KDE conference) in Tallinn, I spoke with Plasma developers who were, at the time, working on a tablet called "Vivaldi", which was supposed to ship with Plasma Active (the KDE 4 version of Plasma Mobile) based on Mer (the community fork of Meego). And they really struggled with the hardware part: They carefully assembled a BOM of parts for which open-source drivers were available, ordered test devices, built the whole software stack. And when they were ready to start mass production, the manufacturer was like: "What, that chip? That's soooo last month. We have this new chip here, which is completely undocumented, but we have an Android driver for you." Last I heard, they never got an actual device shipped because of that mess.
I don't know if it's gotten any better since then, but I can easily imagine how that situation led them to base the new Plasma Mobile on the Android HAL.
Plasma sits on top of the Android HAL like Firefox OS did. Nothing different there. Go buy you QC license and see for how long you'll get blob updates.
You're totally wrong about the performance penalty of FxOS compared to Android on the same hardware, but I'm done arguing that with trollaways.