I just stumbled into the fact that module-shipping requires zendframework/zend-http for its unit tests. So basically if I just want to do the tests of that module isolated (my module depends on that module again), I can't do that now as the requirements are not met.
So my proposal is that every module composer.json should specify the requirements needed to use that module stand-alone (the tests e.g.).
Probably has some impact, but it will improve module development imo.