Good point. It's something that's ripe for standardisation.

If there was fewer formats you'd need fewer repos. Therefore fewer servers and fewer human eyes to review everything.

I'll likely get flamed for this but it would also go part of the way to solving AUR's woes. Have a threat level rating like 1 for safe, 5 for dangerous. Debian won't let you install higher than 2 but Arch users can choose whatever level of danger they can handle.