The only mob I can think of that has native sneak/invis is Shikigami Weapon. No mob has ever cast raise on another so I don't see it happening, as for reraise they could use that bracelet move from Aerns.
They could also just add new monsters in subsequent patches that have the abilities needed.
But it has to be a TP based move in order for Blus to learn it, what mob will use Invis/Sneak to do anything other then run away. Maybe if it was a copy of Camouflage or Hide
I could see it happening, but there is no combat advantage for a TP based Sneak spell.
There is a campaign nm that does this already, but dfoesn't show the JA. He's quite annoying, he disappears, then hits you with a Sneak Attack type hit. If he gets you from behind, it can easily do over 1k.
If they designed another monster with a similar ability, a THF that attacked you from behind, but used an actual JA instead, I could see them adapting that to a full sneak/invis instead of the Hide ability it has for the monster(For example, battery charge does refresh for us but just gives mp to the monster).
Raise to me would be hard if not impossible, but I could see reraise happening in a similar fashion, make a JA for a new monster that does RR.