Don't want SMs of any type on an ANZAC, they don't have the stability reserves for it. What I was thinking about was for the ANZAC replacements that are meant to be significantly larger ships with a large stike length VLS.AFAIK SM-6 doesn't need any illumination equipment so once you have the target track that's all you need to take a shot. It would mean sacrificing three ESSM's in the VLS though.
Again AFAIK CEAFAR and AUSPAR are not the same class (happy to stand corrected here). CEAFAR is lightweight and intended to be used on frigates and corvettes, AUSPAR is an AN/SPY-1D replacement and is intended for use on much heaver ships. I doubt we would see AUSPAR on an ANZAC class.
Not sure about the Merlin AEW's radar but I doubt Seaking could generate a firing solution as it's a 2D system IIRC. In any case you could achieve an OHR shot with any data from an off-board sensor, it just needs to be able to generate a track. Wedgetail would be perfect for this but so would other surface combatants.
If CEAFAR was upto the job I was going to suggest only some of the ANZACs be upgraded with the replacement program being brought forward to allow the retirement of the un-upgraded hulls. Buy the same number of systems, just migrate some of them to new, more suitable hulls.