Chris,

Which of the following would you like me to do?
A. Mail queue utilizes newsletter_drip_send, making newsletter a required dependency of mail queue if you want to use drip sending.
B. Construct mail queue's own separate drip sending hooks and tables.
C. Pull out all of newsletter's drip sending code and turn it into its own separate source / module, which then both newsletter and mail queue will use if installed.

This is a stupid poorly-written-up issue.
The max_queued_mails_per_cron_cycle option was already implemented in https://gitlab.com/composr-foundation/composr/commit/94effd27c9fb25bc1638ebaf0db928617bc9007b

That is all that was really needed.