I think the first question is whether the maintainer can do anything to make the themes optified or whether it is out of their control somehow (problems with the autobuilder etc.)

If they can do something to resolve this, then the themes should be rejected until they meet the criteria of occupying minimum rootfs space.

Extras is meant to be a completely safe (as far as that is possible) environment for non-technical users to get apps/themes/whatever from, hence the reasonably strict rules for entry. Watering down these rules isn't a good road to go down in my opinion.