I honestly just want a skin of any type for him, though I remember playing diablo 2 when I was younger and playing nothing but the necromancer and giving my summons individual names and being really sad when they died (or rather fell apart, not sure you can really make a skeleton more dead than it already is) so a necromancer Azir skin sounds great for this years harrowing, but if they just released a chroma pack for his base model I'd still be happy.
Though on the topic of a necromancer Azir, would his turret just be a gravestone or a creepy undead tower? I think an undead tower would be awesome, you just destroy their tower and poof, now it's all skeletal and weird, it'd be cool.