As a person that's using beorg for GTD (which works great), I don't need or want the ability to delete files from the phone. For me, that feature is 100% risk and 0% reward. I would be a disaster for months if I accidentally deleted my main task list.
I'd like (love!) to be able to turn off the ability to delete files from beorg, either on a file-by-file basis or globally.
There is a way in beorg to retrieve an accidentally deleted file. When you delete a file in beorg the (up to) 7 days of versions of that file remain locally on your iPhone/iPad. If you create a file with the same name as the deleted one, you can then swipe right-to-left on the file, select Versions and then revert to the last version available.
Admittedly this an obvious feature, I'll try and cover this in a learning article on the beorg website soon.
Having said the above I'll add a Scheme variable (file-disable-delete) preventing deletion of files for users who have your particular need.