Pro-active character, that won't break the game.

[Dusk Eclipse]

By design in almost all campaigns characters will find themselves reacting towards challenges, with the monsters/enemies finding them and attacking. Sure there can be exceptions like finding the BBEG lair or grabbing the loot rescuing the princess from the Dragon which allows the character to prepare themselves.

Now one of the Wizards (and spellcasters in general) biggest strength is the access to divination effects which allows them to tailor their spell load, items heck in some cases entire builds (thank you linked-psychic reformation) to counter any dangers, in the same vein this is why they are considered overpowered if not outright broken.

Is it possible to make a character that can anticipate combats or force them to be on his own terms without breaking the game? Bonus point if it can be done with a character with a secondary focus on casting.

[Flickerdart]

You'll probably be looking for something like a sneaky build, who can ambush enemies when he thinks the odds suit him and melt into the shadows when things go sour. Spellthief, Psychic Rogue, or Lurk would be the classes for you.

[Feralventas]

A Bard with a rogue dip going into Unseen Seer (Divination/rogue PrC from Complete Mage) might do this nicely. It puts a fair amount of focus on your mundane skills as well, but it's full casting progression with sneak attack dice and some nice divination buffs. Bard's not overly powerful, but it does a good job as a generalist, so you can prepare to face a number of different things based on what you scry or discern.

Then there's Bardic Knowledge to be taken into account, which is Knowledge (Whatever), allowing you a decent chance of knowing what you're dealing with, and of course Gather Information should be your bread and butter. If you can figure out who's moving where, you can try to take little bits of evidence and put together larger schemes in terms of political events, or figure out what's happening in a large scale area by asking around in various parts of it.

Beguiler can also do this, and has a somewhat higher spellcasting focus, but falls short in some of the more "generalist" areas, so depending on how you want to operate either of these could work. Beguiler can also probably function in this role without Needing Unseen Seer.

Another option that I found useful was a Warlock. Take all of the visual and sense-based invocations. See the Unseen, Devil's Sight, All-Seeing Eyes, and when you get to it Voidsense. Toss a couple Crafting feats on the side for some Detect spells as well, and your party will always have Someone to spot things sneaking up on them. I used this to good effect in a PF adventure path by simply noticing the large, invisible monster in the room. One glitterdust later and we managed to take it down with minimal losses.

[thethird]

Building on what Feralventas mentions one build I've found that works really well being proactive and divination focused without being overly game breaking is:

Spellthief 1 / Beguiler 7 / Prestige Bard 2 / Unseen Seer 10

It gets several divining goodies, and its true power is against other spellcasters so it isn't specially gamebreaking.