"Unit X makes unit Y count as cat A instead of cat B" requirement

[ibboard]

Some units (e.g. Special Characters) allow a unit to be taken from a different category once they are selected (e.g. Algenon the Knight might allow Questing Knights to be taken as Core instead of Rare because his armies always had lots of Questing Knights in them).

This could be achieved in one of two ways - 1) edit the unit on the fly and change the "Get unit types for category" function or 2) the unit is always available under both categories, but the validation is modified to check which category a unit is being added to and takes it into account.