I personally think the Herkladi looks amazing and im extremely disappointed because I cant glamour it onto my Noct lorica (makes me look like im wearing a skirt). My suggestion for glamouring multi-slot armor would be to make us use a glamour prism for each slot it takes up.

For instance:

I will be glamouring my herkladi (takes up chest/hands/legs/feet) onto my noct lorica (takes up chest) I will need 4 armorcraft glamour prisms to overlay the appearance over 4 pieces of armor.

The hands, legs, and feet will not have any interference with the appearance since the herkladi is overlapping it. This gives me the ability to change my hands, feet or legs to another type of armor the I find suitable for my adventure.

If I were to unequip the noct lorica, it will no longer glamour over the other armor slots.

another way to give players customization would be to just split the herkladi into their own chest/hands/legs/feet pieces.