I know Semi autos are legal for IPSC in WA. It does seem close to impossible to get a new one.
The Benelli M4 is one of the best shotguns ever made and given the alternatives are all Turkish made shotguns (which i am sure are fine and good value), they are of course several notches below a Benelli.
How hard is it to obtain an new semi auto shotgun in WA ? You have to import it yourself ?
I know it would be a lot of hassle but if you will definitely get it in the end, i feel it would be worth it.