Can one domain have multiple servers controlled by different entities
Yes, but there will need to be some coordination for getting the SSL certificates
How can the coordination work (depends on the ACME challenge used)
Whenever one of the 2 hosts wants to renew a cert they would need to deploy a
.well_known file to both servers, so that no matter which one letsencrypt access they get the right file.
You can run an additional server, which both parties can push files to, and have both servers redirect any requests for
.well_known to this server
Limiting impact of breaches
As the servers need to be able to generate SSL certificates if they are breached they will be able to generate certs.
Using Must-Staple the impact of current certs leaking can be reduced, but this will not help if the host is instructed to make new certs without this after generation.
Using CT logs you can watch for invalid certs, and using CAA you can limit which CAs will issue certs, which will help reduce the breach impact.
You could even use CAA to disable certs entirely, and only allow issuance by contacting you and manually removing the record until the cert has been issued, reducing your attack window, but increasing the management overhead.