The wizard five-foot-steps away from me and casts a spell: at this point I close and feint, but is it too late to then take the attack of opportunity caused by them casting the spell? And which comes first, the feint or the attack?
And what if the wizard did not move: will the legal part of my action (the feint) still happen? (NB neither of us are Tiny or Fine!) And if they don't cast defensively will the feint happen before the AoO?
Also: what do you think is the right way to keep the GM/players honest if you play rock-paper-scissors with readied actions like this; the NPC wizard could cast defensively if they know you have readied a feint and 5FS if you have readied an attack, and both if you have declared both. Should GM/players declare readied actions on hidden scraps of paper?
And what if one of the combatants has a huge Sense Motive skill and/or BAB: will they see it coming?
Edit: Thanks for all comments. Please consider the dialogue between foxsable and myself before contributing further as I find that very convincing.
Still interested on any ideas (at the "house rule" level) about what it would take for someone being readied against to realise it and act accordingly, other than "He should have gone already on initiative 18, I won't waste my breath weapon on him as he's clearly up to something!"