The recent approval of development of the Kockums Type A26 Submarine. points to some of the features which the Collins class submarine replacement project is likely to consider. These include conventional diesel-electric propulsion , supplemented by air-independent propulsion, a flexible payload lock (an oversize torpedo tube which can be sued for midget submarines and divers), Commercial off the Shelf (COTS) computers, an electronic sensor mast and small crew (as small as 17).
The A26 is designed for coastal operations and would require enlarging for Australian blue water use. The A26 and similar designs can be made longer range by lengthening the ship to add more stores. This can be easily done at low cost with little technical risk. This would involve a trade off in reducing the speed of the ship, to allow for increased range. However, there is a high risk of "mission creep" with the enlarged vessel being filled with expensive unproven equipment, increased power, and an increased crew to operate it.
One way to counter this trend would be to reduce the standard fit out of the submarine, so as to allow for flexible loads. As an example the A26 is fitted with four standard torpedo tubes, as the Australian submarine will be used primarily for surveillance, this could be reduced to two. This would significantly increase the storage capacity of the submarine, while reducing the cost. The submarine would be still capable of carrying the same number of torpedoes, but only capable of firing two at a time.