Effects of Banning Contingency?

[Amechra]

If you straight up banned Contingency and limited CoP and other divinations, how much would that harm a spellcaster's ability to be prepped for every situation?

[Kasz]

Obligatory obvious answer. The caster would be less prepared for emergency situations and have less foresight than he would normally have.

Casters will still be ahead with other immediate action spells / shenanigans but it'll bridge the gap. A Shadowcraft Gnome however will still adept to every situation but it'll be reactive not proactive. (premeditated?)

The characters might be more confused overall... my group uses divination to bridge the gap between clues. Without them they'll be more like... Well Clue A and Clue B both tell us things... but they're not really... connected.

As to contingency replacements.
Permeable Form
Hesitate
Energy Absorption
Halt
Wings of Cover - Included for making Sorc's pretty bad ass.

To be honest... banning contingent teleports makes conjurer's Abrupt Jaunt the only way I know of to gain an immediate action teleport...making an already awesome ACF a little bit better.

In short, it will cause your players to use more resources to maintain awesomeness, or lose some awesomeness. Which is never a bad thing for Wizards.

[Gribel]

Versatile spells such as Summon Monster, Planar Binding and Polymorph become more appealing, since they can deal with multiple scenarios.

[Cyclone Joker]

Craft Contingent Spell becomes even better.

More seriously, it'd make wizards a bit more of a headache, and they couldn't have as many prepped at any given time, but uncanny forethought and the like means it wouldn't be too bad, too be honest. It's be mildly irksome at worst. A minor inconvenience. Wizards would still be gods, and melee still wouldn't have nice things.

[Concerned Ninja Citizen]

It'd hurt Schrodinger's Wizard more than the majority of actual wizards in actual games.

[Nanshork]

It'd hurt Schrodinger's Wizard more than the majority of actual wizards in actual games.

This.  Even in the high powered games I've played in I haven't seen anyone attempt to abuse divinations or Contingency.

[Bauglir]

It's solid theorycraft, but virtually nobody cares enough to actually implement it. We tend to operate on mathematician logic around here. We know a solution exists, and actually finding it in a particular case is usually less interesting than proving the general case

[PlzBreakMyCampaign]

other divinations

What else are you worried about? Without CoP, there is very little I find broken among divinations for combat. They still break the crap out of plot devices/twists.