I completely disagree with the entire argument, sorry if I offend you, but I don't understand your logic.
I am not too familiar with rules before 3.0, but as long as I have been playing you have always been allowed to make a magic item that can do ANYTHING. Whether it is a class ability, racial ability, give you a spell-like ability, or make up a completely new ability. I don't know about items that give bonuses to sneak attack, but there is, the Warlock's Scepter, a published item that grants a bonus to Eldritch Blast
So, no I do not see any problem with this spell. Especially since you have to be a level 8 Paladin to cast this spell. And a Wizard/Sorc at 8th level have Polymorph, which can give all kinds of bonuses.
