Nice ships, but the 2nd drawing (Ikara conversion) is lacking the Ikara missile. I presume the system itself is in the compartment ahead of the bridge.
Yes, I'd forgotten to add it to the template
I think 27-28kts would be feasible, but no more than that.
I'm not adding the 5in aft would be feasible from a trim point of view (though the SM-2 launcher forward might balance things out). There might be space by removing the towed array for the magazine but things are likely to be tight aft. The Leanders were never totally flexible ships, they lacked the growth margin and the space to accept major changes without sacrificing the guns or a decent SAM system. A bigger hull might help, but how much you could push that I'm not sure. After all the T82 began from Leander origins...
Well Hood, from the description of right aft in Friedman that's where I imagined the Australian conversions would mount the 5"/54. I'd imagine you would indeed sacrifice the VDS (As I've done) to convert to magazine space although as you say the well is hardly that big. I suppose you've got the space Limbo once occupied too.