[Q] otg flash drive as external storage

cutting to the chase, im looking for a way to install my apps data and if possible apk files to a otg micro usb flashdrive (its a flash drive that has a micros usb conection that plugs directly into our phones micro usb port.) So far im able to read and write data to it in the sense that i can browse movie files music ect from the usb drive.
What i want to do is to be able to download a app from playstore and it installs automatically to the otg drive.
I tried foldermount and thats fairly inconvenient in the sense i have to first download file to phones internal storage THEN link it to my otg drive, this process is time consuming and irritating for my purposes.
Ive looked into link2sd but its telling me i dont have a 2nd partiton on my otg flash drive, but ive used eauseus partition manager and did that (made a ext 4 , also tried ext 3, partition as part of the overal 16gb flash drive) and no go.

i know this is possible on a custom rom as i did this with a micro sd card many android phones ago.

quick specs on my device
completed stock rooted and bootloader unlocked
latest busybox and su binaries.
no exposed modules or custom kernel.
8gig x1032 singe sim version

any suggestions be my guest.