When the Portage tree eventually gets switched to git I wonder if most of these problems won't go away on their own.
I'm not a developer but I'm reasonably comfortable using git for basic tasks.
So even though the plan is for regular users to still use rsync to get their tree once the switch is complete I plan on using git directly. Then I won't use overlays at all - I'll just maintain my own branch and pull from the sources that I want to use.
The effective barrier for entry will be lower once any user can create a bug report and publish a URL for a git tree that contains his solution for the problem.
Then some people who aren't Gentoo developers for some reason might publish their own trees containing fixes they found useful. If other people found those trees useful they'd start pulling from them and basically the distributed development model could work it's magic from then on.