I just tried a search of major and minor sex chromosomes and found a paper here by Judith Mank who refers to the X and Z as the Major Sex Chromosomes and Y and W as the Minor Sex Chromosomes.
I will therefore refer to the W and Y as minor sex chromosomes, and
will use the term major sex chromosomes in reference to the X and Z.
These terms are based on abundance and do not refer in any way to size
(discussed below) or relative effect. In fact, the effect of the minor
sex chromosomes is, in many ways, anything but minor.
I think I will go with this naming as the hetero-/homogametic chromosomes distinction could become confusing in the context I am using it (Talking about expression of the X/Z in the homogametic and heterogametic sex).
Further I think it is wrong because, while "heterogametic chromosome" would be somewhat suitable for Y/W chromosomes, to call the X and Z the homogametic chromosome is wrong because the X/Z can be present in both a homogametic sense (in females/males respectively) and a heterogametic sense (paired with a Y or W).
Calling the X/Z the homogametic chromosome implies that it is only present in homogametic sexes no less than "minor sex chromosome" might imply a minor role for the Y.
Another suggestion could be to call the Y/W chromosomes the sex-limited chromosomes, but then the question of what to call the X/Z remains... non-limited? shared? sex-unlimited?
Or recombining and non-recombining sex chromosomes.