Of course, in the long run it would be best to have the existing projects run well on the L5. However, there may be a disproportionate amount of effort just to work with any of the upstream projects, compared to rolling your own. Especially if you can get away with some simple scripts and a small GUI wrapper.
Good pointer, and quoting from OP:
@johndoe, I think many useful things could be implemented your way (cropping may be tricky, though). So go ahead and see where it takes you. Whatever the outcome, you will learn something to unlock the next level.
In case you haven’t seen it already, Purism have published blog posts about simple app development based on scripts. These may give a good starting point: