Related question here which gives all the gory details (that I won't repeat in this question), motivations and context.
Can the SD card in a tablet be mounted (e.g. as an Ext4 file system) without the
MS_NOSUID flag? If yes, how?
I am willing and capable of writing, cross-compiling, and building a statically linked ELF executable (for my ARM-based tablet), which is
root-setuid and mixes the features of
sash on my Debian system. I am capable of formatting some SD card (on my Debian) as an Ext4 filesystem. And if I know how to install and run it on my tablet, I will write that program as a GPLv3+ software (in C).
A related question is what exact cross GCC compiler should I use on Debian/x86-64 to target such an ARM tablet.