OK, so I've been rereading the series and developing a couple of crackpot theories of my own. My favorite goes a bit like this:
Varys' given reason for killing Kevan Lannister was because he was being too good a Hand. Varys needed incompetants in charge of Westeros to make it ripe for Targaryan conquest. Now it's possible he was lying, but why lie to a man just before you kill him? That made me think of previous Hands and their downfall:
Tywin - killed by his Tyrion after Varys gave directions on how to find him.
Tyrion - Falsely accused of murdering Joffrey, which had actually been arranged by Littlefinger
Eddard - Double crossed by Littlefinger.
Jon Aryn - murdered by Lysa, at the instigation of Littlefinger.
So we have five Hands, each of whom brought a moderating influence to one monarch or another, brought low by two people. It can't be a coincidence - I think Varys and Littlefinger are in cahoots. I don't have a firm theory on
why yet, or how friendly they really are. One could always be playing the other.
I do have some other thoughts about this. In Game of Thrones, both profess to despise the other and mention knowing things that could harm the other. Now both men have proven willing to remove anyone standing in their way, yet they haven't touched each other. Possibly they are protesting too much?
Additionally I have suspicions about Shae, and also possibly Bronn in all this. Shae most of all.
Firstly she recognizes Varys in one of his disguises straight away, when even Tyrion had been fooled by it. Secondly is the way she makes herself impossible to get rid of even when it was for her own good, and lastly the way she turned on Tyrion at his trial. I think she was sent to Tyrion in order to bring him down. It was well known he had a weakness for ladies of negotiable virtue. Lastly in the chapter where Tyrion kills Tywin, he first finds Shae in Tywin's bed. After killing her he confronts Tywin, and there is absolutely no mention of Shae in dialogue. Tyrion had his mind on other things, to be fair, but Tywin didn't mention her either. Now maybe he was more concerned about the crossbow, and maybe he really was just a big old hypocrite, but I think it's entirely possible Tywin didn't know Shae was in his bed. Varys meant to murder Tywin. Tyrion was the weapon, and Shae the detonator. Maybe they didn't know Tyrion would kill her too, maybe Varys expected it and let Shae take the fall as well.
As for Bronn... Him, I'm less certain of, but here goes. Part of the plot to sow discord in Westeros is to get powerful families like the Starks and Lannisters fighting each other, and Bronn plays a good part in that. First is his meeting with Tyrion at the inn where Catelyn abducts him. Now even though Littlefinger did know where Catelyn was going it would have been hard to arrange for Bronn, Catelyn and Tyrion to all meet at the same inn so this is why I'm not certain about him. But he champions Tyrion against Lysa, thus promoting more animosity between Lannister and Stark and introduces Tyrion to Shae which brings about
his eventual downfall. He then refuses to champion Tyrion against the Mountain. Maybe this was because he didn't fancy going against the Mountain, or maybe it was because Tyrion was now on the out list and so he didn't have to protect him any more. For that matter he didn't protect him during the battle against Stannis. Tyrion would have died if it hadn't been for Pod of all people.
My final theory is how Shae and maybe Bronn got in with Varys. I'm thinking they were ex birds. Varys' little birds are the orphans who go unnoticed. Well orphans grow up. Maybe to become prostitutes and sellswords? Who knows? I may be seeing connections that aren't there.
...OR AM I?