Are you familiar with Apache? You can setup server aliases in the DreamHost Web Panel by using "Mirror Domain" instead of "Fully Hosted", or you can also specify the document root with "Fully Hosted". You can add Alias for url-paths using the "Remap Sub-dir" panel.
As for as email you're stick with adding the aliases. You can bulk edit them though so you could always import a list instead of entering them one by one.
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