This method is tested on iOS versions of the game only! It may or may not work on android.
BFJP Buttons Translation
Make sure you have iFile installed on your iPhone. If not, install it from Cydia.
Download the file named BF IMAGES below.
Extract the folder and add it to iFile using iFunBox or directly in iFile.
Copy the images in the folder you just extracted.
Paste them into /var/mobile/Applications/(BFJP)/BraveFrontier.app
Save and you're good to go!
Remember that this does not translate all of BFJP. It's just a translation of the main buttons and settings for easier access. Please press Thank You if I've helped.