Situational bonus to CMB / malus CMD?

[Doppleman]

In a situation where character 1 asks character 2 to look down a cliff, character 2 now bows to look down the cliff.
Image exemple: http://media.gettyimages.com/photos/wingsuit-base-jumper-getting-ready-to-j ump-from-cliff-italian-alps-picture-id683730303?s=170667a
Would character 1 get a good CMB bonus to push character 2?
I would like to do things like that with my character, but if I need to invest a lot of feats to boost my CMB, it won't be worth.
Maybe it's GM dependent?

[Fuzzy-Wuzzy]

It's up to the GM but this is what circumstance bonuses are for. I believe the GM is encouraged to toss in a +2 (or -2) for random things people do, though I can't find a reference for that.

OTOH Pathfinder doesn't really have a concept of facing, and the GM may not want to set a precedent of considering it.

[Tarik Blackhands]

Situational bonuses/penalties are strictly the realm of GM judgement.

That said in your particular example a situational bonus probably isn't necessary. Since char 2 doesn't appear to be expecting trouble, char 1 suddenly going hostile is probably a surprise round meaning 2 is flat footed and thus denied his dex modifier to his cmd making him easier to punt off the cliff (unless he's dex 11 or below in which case no change)

Regardless though, Pathfinder REALLY does not reward doing combat maneuvers without sinking feats into it so while it's probably fine to bully mooks a bunch of levels under you (and makes for some fun flavor) it certainly won't work in combat.