The activist hedge fund Elliott Management wants changes at (T) Wall Street analysts seem to like the idea. The gains came after Elliott disclosed a stake in the company and laid out several proposals for the board of directors in a letter published as the week began. Elliott, known for taking relatively concentrated bets and publicly agitating for changes at its target companies, wants AT&T to adopt a new capital-allocation plan, cut costs from its operations, bring on experienced management, and stay away from making large acquisitions.