To build UIs that scale well for large numbers of objects, we will not be able to use the default combo box elements supported by browsers because they have limited searching and lazy loading capabilities. Instead, we should create a reusable component similar to the one used for account switching in OXP that would allow to quickly choose one entity out of many, either by search, paging or picking a recently used item.
The component must be easy to work with within forms (rendering, submission, validation) and as a standalone widget. During implementation we may either re-use the OXP account switcher, adapt some of the jQuery plugin components or, if reasonable, roll our own.
The drop down will be required to implement forms containing parent entity selection, user switching and the dynamic menus ("Add tracker for...").