A customer has a handful of accounts that have a key account manager but other account managers still need to be able to see these accounts as well. With the current account manager restrictions you can only view your own accounts. There would need to be a system option to mark certain companies as 'Shared' accounts that everyone got to then see.
This is now available via the new Territory Restriction feature (if you aren't on this version yet, dont panic, it's being rolled out).
See https://app.intercom.com/a/apps/e2etkajo/articles/articles/5723586/show