I think WPMU Dev have a niche market that is not yet being tapped with a search & results presentation plugin.
Especially a search plugin that would work with Custom Press / Directory and your other plugins for events, markepress etc.
Specifically a search plugin that can:
* provide different weights of results (a standard search optimisation feature)
* provide a filter search form box of custom taxonomies and the like.
* provide paginated search results in a specific layout
This would be a powerful plugin to offer as it would do the above three things together.
Currently most search plugins only offer the first feature .. like relevanssi or search WP. They require extensive custom work to integrate in terms of presentation of results and the ability to do filter search forms.
. . .
I would like the ability to have a search plugin that helped to create a single (or multiple) custom post type search box. Within that search box have the features to add custom taxonomies as check boxes / radio buttons, multi select list or dropdown list. Then be able to filter the search results based on the text box field as well as the taxonomies.
This is a massive wordpress feature that very very few suppliers are doing. I only know of one: the Views plugin by http://wp-types.com/ which still requires a lot of custom development knowledge if you wish to check that content is there before showing that content field and other things besides.
This is a HUGE feature / plugin request I know but its the the opposite side of your custom press plugin coin.
I would love to see you develop this as a plugin offering. What do you think?