Michael, you’re the one who has to maintain this ebuild, not the user who submitted it. So making it maintainable for you is what’s most important. Whether the submitter thinks a six-line sed is easier is completely irrelevant, because the submitter isn’t the maintainer. And even if the submitter is temporarily the maintainer, committing through you, that won’t always be the case — at some point, a developer will have to deal with it.
That’s how I’d think my way through your conundrum.