For the obese tag, we have the following modified tags:

obese_male
obese_female
obese_ambiguous
obese_intersex
obese_anthro
obese_feral
obese_humanoid
obese_taur
and etc

These tags tend to be used pretty sporadically.
To improve the rate at which these tags are applied, they could be added automatically where sensible

For example, if the tags obese, feral, and solo are all present on a post, logically the obese_feral tag should also apply.

This same schema could also apply to basically all tag_[sex/form modifier] situations.

So essentially I'm looking for input on why this would/wouldn't be a good tagging situation to automate with the following logic:

if [obese] and [sex/form] and [solo]:

    add [obese_sex/form]

This definitely may cause issues in certain situations, but I'm not sure.

Alternatively, the modified tags could just be removed from all posts tagged solo, since their utility is (afaik) limited to posts with multiple characters.

Considering that lots of users don't tag body form gender, and character count correctly, this might be a bad idea.

This isn't a bad idea necessarily, but there's a number of posts that incorrectly use both slightly_chubby and overweight/obese in combination to describe the same character so automating like that is probably a bad idea for now.