Australia's multi-billion-dollar deal with Japan for its future warships could set a template that will help Tokyo rapidly expand defence exports across Asia as Tokyo mulls an overhaul of its post-war pacifist constitution.Last weekend, the federal government announced it had signed a contract with the Japanese conglomerate Mitsubishi Heavy Industries for the first three of the 11 upgraded Mogami-class frigates.Japan frigate deal for AustraliaDefence Minister Richard Marles and his Japanese counterpart, Koizumi Shinjir?, signed the deal aboard one of the warships docked in Melbourne. Days after the announcement, Japan loosened decades-old restrictions on defence exports, in a long-anticipated change that will…