Hello,

creating loops from a single file could be another useful extension.
At least I need it quite often for seamless looping on some signage mediaplayers.

By now I use ffmpeg directly with a file containing the input filename multiple times:
i.e. /list.txt:

file 'test.mp4'
file 'test.mp4'
file 'test.mp4'
file 'test.mp4'
(...)

and then:
ffmpeg -f concat -i list.txt -c copy output.mp4

Greetings,
himi