- πͺπΈSpain penyaskito Seville π, Spain πͺπΈ, UTC+2 πͺπΊ
Seems that there's some agreement on #6, which I added to the issue summary.
But as a 11 years older me, I remember lots of pain giving support to customers with hundreds of content types and hundreds of fields which had timeout issues, or POST request size issues on admin/config/regional/content-language. The workaround on that case was hacking the config files (not recommended for not-advanced users), or indicate to go to each content type and each field and mark the relevant checkbox.
So I think
content_translation_form_language_content_settings_validate
is a much valid approach, and/or even having a config schema validation constraint for this.