Exchange Online to introduce External Recipient Rate Limit

We are a large health organization, and these limits are going to impact us in a negative way.  We understand keeping the reputation of the Microsoft IPs intact etc but when you have hundreds of thousands of staff and millions of patients, 2,000 of anything is a drop in the bucket.  Many of our clinics have more than 2,000 patients and have a legitimate need to communicate with them easily through email.  Many send from shared mailboxes to patients.  ACS will be difficult to implement - both with the rate limits and the problem that only external emails can be used.  We have no way to separate messages being sent to ONLY external recipients (staff are also patients - and sometimes they use their work emails...)  Plus, we literally have thousands of teams sending out email.  We also support many 3rd party sending applications, but we worry about security, and it adds to the complexity of our mail setup.  We want to keep email sending from our own organization so that it can be audited and tracked.  These types of limits will only move email out of our Exchange Online tenant and create a lot of work and potential security risks for us.