the Jester said:
I like the variants in UA; I would recommend just giving them those bonuses for free if you feel they need a power-up.
On the subject of diviners, I have always thought that a well-played high-level diviner is certainly powerful enough to warrant banning two schools of magic; I don't think they should get the special treatment of only having to give up one. Angel of Adventure's cohort in my epic game proved me right; a powerful diviner is a fantastic asset.
I think it depends heavily on the campaign and the plots given, and on the spells actually avaible for the Diviner. My experience tells me that the PHB spells offer some very basic abilities (and you can't go without them), but they aren't exactly powerful. If a diviner had access to some divine divinations, that might be different, but the wizard spells aren't that impressive.
That said, I think you could still give up two schools. You don't need illusions or enchantments, even if they are very versatile and offer some interesting abilities. In role-playing heavy campaigns they might be a lot more interesting (but I somehow don't like the idea of using Charm Person or Dominate in such campaigns), but in a straight dungeondelving campaign, abjurations, conjurations, divinatons, evocatons and transmutation are sufficient.
What I would consider for specialist wizard:
Grant them access to non-wizard spells. Maybe they need to specifically research these spells (no freebie per level and no simply copying from a scroll), and maybe at a higher level as it is available to other casters. Unfortunately, not all schools benefit identically (Conjurers and Diviners probably would gain the most of it, and the latter might be especially problematic with the fact that they have to give up only one school.)
But I am currently really considering to have my next wizard (whenever I will need one) be a generalist. I think the extra spell slots are worth a lot to a wizard, but being able to cast really any kind of spell is nice.
(Though I must admit such a Generalist quickly has to become a Loremaster, and I don't want to play a third one.)