In most international projects, there is a need for translations for referential data.
Typical Business Case: need a list of Countries, with their ISO Code, Telephone Prefix, ISO Abbreviations, etc.
Option-sets are *not enough* as we cannot set any additional property on an option-set, as we would on a custom entity. Furthermore, when integrating with a third party IS, we often do data transfers and option-sets are not appropriate. For example, w often need to integrate referential data from SAP (countries, payment terms... etc.) that can't be natively properly translated in Dynamics CRM.
My suggestion: => Enable translation of the primary field (text field) of entities that are used for referential purposes.
I guess this could be achieved similarly to what you did for products.