What you want to do can be done but not using the basic release and standard themes.
If you have the budget, such linking can be implemented by customizing a theme and using plugins.
Let's consider using a Person's name in the creator field and have that lead to the item in the Person's collection.
The name is the value entered into the creator field.
The same name is the one used to uniquely identify the person in the person collection.
This has two distinct issues: uniquely identifying a Person by a name, and linking to the right item in another collection based on the value in a metadata field.
Identifying a particular person by a name is not trivial.
Does the data set of Documents have a well defined set of Creators?
If so, then it is possible to create an authoritative set of unique names that identify each person. Using that value as the Title field in the Person collection and as the Creator field in the Document collection allows looking up the specific Person who created the document.
If the set of creators is not well defined, it will be more complicated. An external source of unique authoritative names might need to be used.
There are a lot of considerations when working with names. How to display them? How to sort them? What is the form that is the authoritative value?
These lead to many questions about the limitation of Dublin Core's Creator field.
Considering such things is all part of making the Person a first class object in the collection display.
Keep in mind that the Dublin Core metadata is there for sharing the digital collection with an external indexer or consolidator.
It is not there to support local models on how to showcase the collection.
If there are specific features needed in the collection display that require having more metadata for an object, it is easy to define and register the need to capture the extra metadata elements within Omeka. That extra data can be entered and stored with no added development work.
The added features are implemented with code in the themes and plugins that use those extra metadata elements.
If a Person becomes an important object, then there may be a need for several metadata fields to hold the "name". One to hold the common informal name, "Joe Hill". Another to hold the value used for sorting, "Hill, Joe". Another to hold the authoritative value used to uniquely identify the person, "Hill, Joseph".
The plugin "Search by Metadata" is a good one to help build links to related items. It could be modified to work for the case we are considering. As it exists today, it finds other items having the same value in the same metadata field, for instance other items created by the same Creator, across all the items in the Omeka system.
What is needed is a way to use the value in the Creator field of one item as the lookup criteria to find the one item in the Person collection having that value in another Metadata field, such as Title.
How will the data be entered into the system?
If it is entered by batch processing where all aspects are controlled, then data entry rules can be enforced with less work. A document's Creator field value must be exactly the same as the Title field value of the Person.
If the data is entered by hand using the Omeka data entry interface, by various people, then additional design and development is needed to build a data entry system to enforce correctness.
What is the user interface for linking between a Document having a Creator value and the item in the Person collection?
If there is a simple link from the Creator field value, shouldn't that link be to a page browsing all the Documents having the same Creator?
The link to the item in the Person's collection would need to be a different link.
For each Creator, there needs to be two links. One to the item in the Person collection and one to browse all Documents created by that person.
Showing those two links is part of the changes done to the theme files.
Having just two collections, Documents and Persons, may be a wrong model. It is possible that the Documents have groupings that would map to several collections nicely, such that there are multiple collections of documents and the special Person one.
Does all this give you encouragement to pursue your plan?
It sounds like a nice model for showing the collection but it does require a budget to customize themes and plugins.