I ask it because you can deploy unlimited xap files to your phone.
All you need is the latest WP 8.1 update and a phone with a sd card slot.
First you can Developer Unlock your Lumia phone to be able to deploy 10 xap files.
Deploy 10 apps to your phone. After that you can move your 10 sideloaded apps to the sd card with the storage check app.
After that remove your SD card from your phone and deploy other 10 apps to your phone.
Now you can insert your SD card and move the new installed 10 apps to the SD card.
After that you can reply this process again.
With this method it should be possible to deploy unlimited xap's to your phone.
Hope this will help the devs to Jailbreak a Lumia like the 1520.