Let me reply one point after another...
Arafura class looks nice, however her short-legs (4000 nm, 21 days) and diesel propulsion do not tick the boxes. As far as it's based on Lurssen OPV-80, going one step beyond to OPV-85 would add hangar, electric drive and maybe higher endurance at the cost of about aditional 300 tons (total 1900). This being all theoretically, as these ships are always tailored to customer request.
The OPV 85 Offshore Patrol Vessel is a versatile, flexible and tailor-made platform to meet a wide range of demands in territorial waters and the EEZ.
luerssen-defence.com
Second, a crew of 30 for a MCM vessel may be ok, but, not being an expert, I believe not enough for an OPV.
I may agree to the 30 mm gun, considering that MCDVs are performing their roles without their original 40 mm guns. However the Arafura shows a 40mm... there must be good reasons for that.
Finally, new Hueys (UH-1Y, about 8 tons) may well be the solution, despite I was rather thinking of smaller helicopters (bell 412 or 429), including also Wildcat or the new Airbus' H-160.