Introduce new arbitrary object key/values data structure for persistence of Tika Metadata

I am currently working implementing more comprehensive extraction and enhancement of the Tika support for Phone number extraction and metadata modeling.
Right now we utilize the String[] multivalued support available within Tika to persist phone numbers as

Metadata: String: String[]
Metadata: phonenumbers: number1, number2, number3, ...

I would like to propose we extend multi-valued support outside of the String[] paradigm by implementing a more abstract Collection of Objects such that we could consider and implement the phone number use case as follows

Metadata: String:  Object

Where Object could be a Collection<HashMap<String/Property, HashMap<String/Property, String/Int/Long>> e.g.

Metadata: phonenumbers: [(+162648743476: (LibPN-CountryCode : US), (LibPN-NumberType: International), (etc: etc)...), (+1292611054: LibPN-CountryCode : UK), (LibPN-NumberType: International), (etc: etc)...) (etc)] 

There are obvious backwards compatibility issues with this approach... additionally it is a fundamental change to the code Metadata API. I hope that the <String, Object> Mapping however is flexible enough to allow me to model Tika Metadata the way I want.

Any comments folks? Thanks
Lewis