Get rid of this archaic tri service set up which wastes so much infrastructure.
The Canadians did this and it hasn't been a great success. I agree with getting rid of a lot of duplication but I'd advocate getting each service to do what they do best, ie all vessels including landing craft should be maintained and supported by the Navy, all aircraft should be maintained and supported by the Air Force and all land based defence activities (including RAAF Air Defence Guards etc) should be done by the Army.
The British are currently building two large aircraft carriers but the Royal Air Force will "own" the aircraft that are deployed on them. The crewing of them will probably be a 50-50 mix between the RAF and RN but the maintenance and long term support will be done by the RAF. This came about because the RN displayed an inability to develop the Sea Harrier throughout its service life - it had the potential for significant gains in capability mainly through software development but the RN didn't have the infrastructure/personnel to drive these improvements. The RAF has the infrastructure and experience to ensure that the JSF will continue to develop throughout its service life.
I believe that Air Force maintainers have a better focus on all things aviation whereas the Navy aircraft maintenance staff are split between naval and aviation interests. Similarly, the army staff who carry out helicopter maintenance have impressed on them that they are soldiers first and maintenance engineers second - the system results in a fairly high turnover rate and thus overall experience levels remain low.