I've been looking for a mod that removes the rocket capacity line from items, the mod settings say it gets rid of "too heavy for rocket" but the rocket capacity remains, is it possible to remove that also as a feature?

Unfortunately I didn't find a way to remove that. Py doesn't take weight into account at all and with the complexity of most recipes, nearly all end up being too heavy for a rocket. I just set the weight such that the capacity would be the same as the stack size which felt less bothersome.

If I were to speculate, that text might only show up with a specific feature flag (like space travel) which Py doesn't use, and that an alternative to the Enable All Feature Flags mod without that feature flag would do the trick while still allowing the features it does use.