AT&T was so confident in the incompetency of US regulators that post-merger plans were already laid out, ready and waiting to be called into action, just days after official approval was stamped on its $85.4 billion takeover of Time Warner. The merged entity’s opening gambit will be highly disruptive for not just the TV ecosystem, but the mobile market too – which is sure to be first of many carefully dissected strategies. CEO Randall Stephenson outlined his plans for a mobile-first strategy centered around a new $15 a month skinny bundle offering called Watch TV last month, speaking at a JP Morgan conference. Stephenson also spoke about a free version and this was confirmed late last week, speaking to CNBC,…