But all the fashion these days with carriers and large amphibious ships is to remove all weapon systems from them. Nothing at all. They are dependant on escorts for protection the use embarked aircraft. I would be quiet happy to see no weapon systems on the BPE bar a maybe a few mounted light machine guns or at most ciws, but I doubt you need either. Including them pushes up crewing requirements, costs, reduces space that can be used for its primary missions. The LHD has limited room for weapons (small area up front and at rear). Your talking Cwis or light machine gun, not missiles.
It would most likely be escorted by aleast a destroyer and perhaps a frigate or two depending on the mission. It is not a ship you let wander out alone. On more risky missions I can see it being the centre peice of a multi national force, with maybe as three destroyers (OZ, UK, US) , half a dozen frigates and a few nearby subs. Perhaps one or two HSV's or/and littorial combat ships. Forming a Amphibious Strike Group (or Amphibious ready group). Any weapons the LHD has will just get in the way and take up valuable space.
I would rather the money spent on either getting 4 destroyers or beefing up the destroyers and frigates. There is space and man power on these ships for additional upgrades. Given our few surface units each of the destroyers/frigates should be moving platforms of unchallenged regional power. SM-2, SM-3, Harpoon, Tomahawk, 80+ tubes, CIWS and/or RAM. With 4 destroyers you could double your destroyer escort (2 Hobarts) meaning hostile operations could be conducted without international assistance.
With 1 or 2 Hobart destroyers and 2 upgraded Frigates and a submarine nearby it would be hard to see how that is inadiquate protection. Anything the LHD wears is just for show.
It could also be argued if the destroyers are not going to operate without either the LHD or a frigate then aircraft facilities are not really needed making room for more firepower. However I would have to look very carefully at that as a small force we would want to stay flexable.
As a full carrier it would be helpful to have other ships nearby able to conduct helicopter flights. Freeing precious deck space for fixed wing operations.
For Australian purposes, I hope they keep to the origional BPE design as much as possible. Free and flexable.