No, it is not possible to create subdomains of a domain that is on one DreamHost account under a different DreamHost account.
The only situation where you should be in control of multiple DreamHost accounts is if those accounts correspond to separate businesses or organizations you manage that all happen to use DreamHost. So long as these organizations are actually separate from each other, I cannot see any reason why they would need to share domains in this fashion. (If they are actually so closely related that they share domain names, they should probably be on the same account.)
If your site needs more resources than are available on a DreamHost shared hosting account, you can (and should) upgrade to a DreamHost VPS or Dedicated Server. It is possible to split domains and subdomains across multiple servers, so long as it remains within a single account.