If you haven’t already, you might float out a request on the Omeka designer/developer marketplace forum.
I’d say it’ll also help to define a sense of what kinds of building / customization you anticipate. Much can be done via the admin UI and shortcodes. Theme tweaking and customization is a different story, and customized behaviors via plugins are yet another.
In general, a good starting point for knowing what you need Omeka to do and what customization might be called for is to figure out, for your corpus, what defines an “Item” in Omeka, and whether the user interactions you want are available out of the box. Then, there’s looking at the existing plugins to see if they get what you need.
The other thing is whether you want a custom theme, or can make little tweaks to an existing theme that gets the job done for you.
Hope that helps,