Effort is put into defining Personas that provides the relationship to product and feature - this is constant and should not have to be multiply inserted. In developing a Feature, for example, it is essential that the developer is aware of and uses the defined relationship.
Adding this as a Link properly represents the formality of the relationship - fundamental to the information model, not merely an attribute to attach. This then also enables the built-in visualisation to provide clarity to stakeholders on the manner in which their expected role needs are being met in the roadmap.
This particularly applies when mapping Personas to key business stakeholders in the development of features (and of course, strategy and releases).
The existing relationships are probably sufficient, as these will allow use of the existing mapping representations.
It may be worthwhile considering allowing specification of custom relationships to better reflect implementation of roles. This would integrate if it were implemented such that the existing relationship definitions could have aliases. e.g. there are multiple meanings possible for both 'depends on' and 'impacts on'.