Do you think Tywin plotted with Denys Darklyn to lure Aryes to Duskendale? It seems ridiculous that Darklyn would risk the extinction of his House over a charter.

If so, it would have been incredibly risky – given how badly Lord Darklyn wanted that charter, why not sell out the Hand who’s not getting on with the King in the hopes that you get that charter as a reward from the King? 

If Tywin had a plan, I think it was a lot simpler. From the WOIAF, the beginning of the Defiance is described thusly:

“It was Lord Denys’s desire to win a charter for Duskendale…this did not seem to him such a vast demand…yet it was understandable that Lord Tywin, as Hand, firmly rejected his proposals…infuriated at the refusal, Lord Darklyn then devised a new plan.”

Why did Lord Darklyn think it was an easy lift, and then get so pissed off when he got turned down? One possibility is that Darklyn had been told ahead of time by a deniable intermediary that everything was kosher, to raise his hopes and increase the chances of a rash reaction. 

Then all Tywin would have to do is to work a little bit of reverse psychology on Aerys II.