Every company requiring this type of functionality I'm the non-nostr world has to run a 'server'.  Sure they can get free up to 10 seats from Google or whatever to have their employees send email from their domain, but that's not really free that's a trial of a paid server.  Nostr is no different.  If you're a company you should probably have a relay suite, and this server acts much like googles suite for your company.  It can have extra features there like, keeping company notes, running bunkers, have apis, manage nip05s, run bots etc.  So as nostr:nprofile1qqsrhuxx8l9ex335q7he0f09aej04zpazpl0ne2cgukyawd24mayt8gprfmhxue69uhhq7tjv9kkjepwve5kzar2v9nzucm0d5hszxmhwden5te0wfjkccte9emk2um5v4exucn5vvhxxmmd9us2xuyp said, it would be easy to have a bunker or API to handle the access to a single company key and revokation would be instant.

The eventually inconsistent nature of the public nostr network is not going to be able to come to a consensus on something like a key rotation.  Just like delete is in the spec, the deletes are very hard to propagate.  The same would be true for any attempt to revoke a key.  

However, the NIP87 spec for private groups does do key rotation for a private group, but this requires the group to be on a limited number of relays as part of the spec.  Perhaps delegation could work this way, but the reach of the notes would be limited to a set of relays.  Notes would be more relay specific, and a combination of outbox and relay specific notes would need to be implemented in clients.  At which point you would likely still want to run a relay for the company, but you could 'trial' the functionality on any set of relays that you trust enough for your purposes.