> Merges to main should not be more than 150 lines long

This can be done by allowing a flag in the commit message that bypasses the 150 line long (or whatever example) rule in the CI that enforces it. Then the reviewers and submitter can agree whether or not it makes sense to bypass the rule for this specific case.

In many cases like this, it's okay to override a rule if the people in charge of keeping the codebase healthy agree it's a special case.