AC has LMU. The problem is that one can never find out if it will be offered and the price. It's "all over the map".
For upgrade with points, "I" inventory is required, not P or Z or R. It is very difficult to find on many routes. They should be the same as eUpgrade IMO.
Unless one truly needs the "flexibility" of a Latitude fare, very often, buying a discounted business class fare makes much more sense even after factoring in the costs to cancel or change.
It used to be one of the best perks as an upper tier Altitude member to be able to fly business class at the cost of Latitude on a confirmed basis, not having to play aerolotto. This is no longer the case in many situations with AC's current pricing structure. For North American travel, I often find other airlines' F/J fares cheaper than AC's Latitude.