The argument for a guaranteed wish seems to be that it would make ultra endings less of a hassle to complete - is that even desirable? If you set your mind on it, you can already complete an ultra ending fairly reliably, thanks to the Darkforge pools and the Casino. Fixing the Casino would shift that somewhat to make it harder, but that doesn't seem like much of a problem to me, either, since the AoLS is the true bottleneck to begin with.
Even if you perceived the scarcity of some of the ultra ending target items as an issue, it's always preferable to fix that issue with a specific solution rather than a catch-all. If an AoLS is deemed too hard to get, build a quest around it. If the scroll of danger is an issue, put it someplace fitting and secluded; since it's a crap item in itself, you don't even have to build a quest around it. Those seem like much more flavorful and less potentially disbalancing solutions than a guaranteed wish. Once you place a guaranteed wish on the map, the scarcity of non-artifact items becomes a non-issue, and the item-collecting minigame that is part of the hack'n slay experience becomes much less enticing.
EDIT: (How about putting the AoLS on a mini-boss? Only way to save it - along with halving the duration of the fight - is pickpocketing it before you kill the guy. Benefit of that would be that you could fix Pick Pockets and keep it useful!)