Lyxen
Great Old One
If they are, they can do the customisation, and if they are not, they are probably not interested anyway. I think WotC did the right choice of leaving the DMG light in terms of options, I would even have removed a few more of them, but considering the sales of 5e, it's hard to criticise...It's the sort of world building advice that would actually be useful in the DMG. Not everyone is an expert on historical weapons and armour.