Install custom system, on unlocked bootloader
I got it to work with install another system on the phone !

Model phone MT6570

step 1:
Download: https://www.needrom.com/download/blu-studio-j2-s590q-2/
step 2:
Format the hole phone (with MT6570_Android_scatter) from step 1
step 3:
Load the new (MT6570_Android_scatter.txt) from the step 1
step 4:
From the real Firmware (https://www.needrom.com/download/i11-pro/)
step 5:
Change the real preloader, lk, boot, recovery, logo, md1img, secro, cahce, userdata
step 6:
Load the system.img from step 1
step 7:
Wait for boot up


Hope the helps other :)

It works for me !