@Mr.Nona: Yes, I added the jewels in the "extremely rare" items you can get with Hot & Cold. There are other jewels in the other Chocobo places (I think you can get Diamonds, Emeralds and Moonstones; I don't remember if I also added Rubies in one place). Honestly, this change was not long-considered for balancing or other purpose: I only found it funny to imagine a completionist trying to get 99 of those jewels as ultra rare digs. I must admit that the game is quite sadistic against hard completionists and I didn't do anything to make it better ^^'
@Nikkolas: No, I have only tried once to do Oeilvert with Eiko, Vivi and Dagger in vanilla and it wasn't too hard, just more tedious. You can still do some damage with Zidane and rackets. In the mod, I guess it mainly depends on who can access to Clear Headed at this point (if none of them can, then it must be a terribly hard fight).
Taking only one magician is not a problem though. Speedrunners usually take Eiko with them for Ark and that doesn't disadvantage them so much. Valia Pira can be beaten with any party, as both physical and magical abilities are useful in the Desert Palace.
Also, Oeilvert is the point from which you can get dead peppers. It's a very strong damage dealer when doing a lvl1 run (especially in the mod).