I am not against a cloth wearing, ranged caster Necromancy themed class, but I just can’t see them creating something that is much different than a Warlock, while still retaining what you want a “Necromancer” to be.
As it is, this would just step on a lot of toes to create something that is just not all that unique. I agree with others; giving the option to reskin demons/spells for Warlocks to give a Necromancer feel might be the best route. No toes stepped on, and you get the theme you would like.