Could you trick a smartphone into thinking it is a PC, install regular Windows and use it as a normal computer? How would you go about it?
The ASUS Zenfone 2 can run Windows 10.
The first problem you will have for most smart phones is the processor is from the wrong family. The ASUS Zenfone 2 gets round this by being a bit of an odd phone as it is x86 not ARM based. But you could using the ARM version of Windows (reducing the number of apps) or an emulator (slow).
Next issue you will face is the bootloader. All smartphones are locked down tight to only run the OS allowed. The Zenfone 2 gets round this by using the virtualization tech on x86 chips. I've no idea if the same thing could be done on a ARM. In theory you could bypass this.
Next you have drivers to deal with. GPU, WiFi, mobile, storage and touch screen are a must. The Zenfone 2 using largely stock x86 kit would have less problems here, but I'd guess virtualization has handled most/all of them. It is fairly likely the kit in an ARM device does not have drivers for Windows 10.
With all this you'd end up with an underpowered device. It would be cool (I would have bought a Zenfone 2 had I known about it 2016) but quite slow. Someone mentioned cooling as an issue. I suspect it would be fine for light tasks (same as a 7″ Windows 10 tablet).