Thank you everyone for posting on this thread!
for Bastoche:
it seems that in my group the Cleric is the most wanted Class!

But I stressed the facts that a party must be most of all balanced (and that Good and Evil Clerics don't get along well), and so they are just a couple at the end
I think that a spell required to craft a magic item can be provided in very many ways, not only by preparing it, but also using scrolls, wands or staves, and of course also with a Limited Wish / Wish or Miracle. It is not very handy, since it requires anyway to be 17th level (18th for a Sorcerer - 13th/14th for Limited Wish) and spells over 7th level cannot be replicated by anything. But Clerics are in a better position anyway, both because Wish doesn't replicate over 6th and because Wish costs 5000xp and Miracle not. And don't forget that Wizards have to spend gp to learn new spells.
Of course you can be aided to provide spells by someone else, my discussion was intended to focus on the single PC's abilities (of course, in practice it is levelled by cohoperation). But in my opinion it is still the Wizard who should be able to do a lot counting only on himself. Am I biased?

Anyway, there are a lot of items that require both Arcane & Divine spells, so they do need or cohoperation or being multiclassed.
BTW, does anybody know how to post I file on a thread? I have this excel file with items and requirements and someone might wish to use it (although it is far uncomplete...).