This might be a dumb question, but why? There’s a great big flex space in the middle of the ship that could be replaced by a serious number of VLS if you’re willing to sacrifice it.
Obviously some very important questions about stability that need to be solved, and some complex redesign work to be done, but why would this take more than a couple of years to resolve?
Such a change would likely seriously change a vessel's displacement and very importantly, displacement distribution and CoG, as well as all the potential issues with launching missiles and the requisite clearance and hot gas exhausts.
If one looks at this
YouTube video of a model of the
Hunter-class for the RAN, what I take to be the flex space is amidships aft of the funnel but forward of the hangar. Without more exacting diagrams or pictures it is hard to determine specifically, but it appears that the bottom of the flex space volume starts below the level of the deck where the Mk 41 VLS is forward, but likely well above the bottom of the Mk41 VLS which IIRC would penetrate something like two decks. It might be possible to replace some of the flex space with a VLS, but that would either require rearranging this because either space currently used beneath the flex space would be needed for penetrating VLS cells, or the whole of the flex space gets used which puts a VLS amidships but well above the waterline. Given the topweight issues experienced with the
ANZAC-class frigates, I do not think it a good idea to attempt to shoe-horn a decently sized VLS into such a space. It would be a much better proposition to have a 2nd set of VLS cells put into a dedicated position in a purpose-made design. If one looked at the USN's
Arleigh Burke-class DDG's, which do have two sets of VLS cells, one fore and another aft, such positioning makes more sense to me, instead of attempting to launch missiles from amidships between superstructure spaces in used by a vessel.