Yes, it is possible... but is very dificult.
I studied some new controllers and everyone has the pins signals "write-protect". Even on PCB there are circuited printed who connect that pin. Even if it works on "low level" (pin put to -voltage) or "hi level" (pin conect to +voltage) the circuit must be there and theoretically it can be interrupted and mount a hardware switch.
But... whet you take a closer at PCB and the pen case you will see that is almost imposible to mount one. There is no space to mount one, maybe only if you can build another case.
Also this pin works "write-protect" on whole flash-disk, not only on one drive (partition), if you have more than one. The software switch is very safe as long it programs controller not to write to memory. It is the same thing like a hardware switch but the advantage is that work on every drive you have on flash-disk.
In my situation (UT163) you can protect drives but after that you must format the disk
On MPtool for UT163/UT165 you can notice the steps:
chkblocks ->
update USB info -> stress -> format
These steps are done automatically... Why not interrupt the process right after 'update USB info'
, because here the controller are programed to read-only one disk. I do not need everytime 'stress' and 'format'.