Not gonna fuss around with quotes, and apologies for the slow reply. Had a lot to do in the previous few days. Pretty sure you can match up each of these points to the relevant quote, though.
I really like Vicious Mockery for Naberius. As you said, very thematic, and it's a pretty good cantrip with an uncommon damage type and inflicting disadvantage. Seems like Naberius binders can take a kind of support/debuff role in combat with VM and Command, and that's neat.
Dunno about only one vestige granting extra attacks, but I do think if there are multiple that do then they have to not stack. I do like the idea of "if X conditions are met you get a bonus attack". Maybe give Paimon something along those lines, perhaps something that fits the same kind of role as Mobile? If you hit an enemy, they can't AOO you and you get an attack you can use against a different enemy?
I'm really liking the Naberius rework. Going to go through each feature below:
Flavor Text: Not much to say here, seems similar to the 3.5 version.
Proficiencies: Good. Fits with the existing fluff on Naberius and skills, and from a mechanics perspective lets you do some additional crafting stuff with the rarer artisan tools.
Leverage: I really like this. Advantage is strong, but it's balanced out by the conditions/limitations. Very fitting of Naberius, IMO.
Naberius's Snarl: See comments on VM above.
Disguise Self: This works well, I think. Nice middleground between "at-will in-combat disguise" and "i need to short rest to swap disguises". Requires some forethought on what you're going to do/who you're disguising as.
Persuasive Words: I also believe I talked about Command in a previous post. Addition of Suggestion fits with 3.5, but the requirement of both a certain binder level and a certain vestige level strikes me as kind of odd. Dunno your reasoning behind it though, so it's probably like that for a reason. Care to elaborate?
Pact Information: See Flavor Text above. Somewhat reminds me of the background-specific Flaws.
Other stuff: I think this new Naberius is certainly a step in the right direction. Keep going with it. Interesting ideas on Paimon as well. My take on his Dance is up above. As for Amon, besides ram horns and fire I'm not sure what direction to go with him. The anti-Binder stuff is an interesting take, especially given his dislike of some other vestiges.