i've just recently wished to be able to customise grub without accidently messing it up (and well I really have no experience with grub customisation).
After a bit of googling I stumbled upon grub-customiser, but I remembered that you really hated it for being a buggy mess.
So here comes my suggestion: How about creating a non-buggy version of grub-customiser that is bundled with the grub config editor?
I'd love to help!
(Here is my current project so it doesn't look like I don't know what I'm getting myself into)