As I was told in my recruiting process we usually don't just fix up ebuilds of other devs unless it's trivial, very severe or something.
The usual process is nothing new: try to contact the maintainer, open a bug, set a deadline when you will go and fix yourself. Only question is now what is a sane soft limit, before you go on and fix stuff. >From a discussion in #gentoo-dev we thought 2-4 weeks depending on the severity of the bug is fine. Ofc this should exclude major changes or delicate packages from base-system/core/toolchain. I tried to document that a bit: https://bugs.gentoo.org/show_bug.cgi?id=445402 any objections? This is nothing new, just a clarification of already existing policy and a reminder.