Best off to contact CASA and find out exactly. I don't think there would necessarily be an issue but don't make decisions based on anonymous opinions on an internet forum!. The aircraft would need to be certified to operate door off and any restrictions in the flight manual/certification on that would need to be observed. I think CAO 29.5 still applies
https://www.legislation.gov.au/Details/F2015C00054
I would however contact CASA directly and make sure what you are proposing is kosher and what exactly you need to do to comply with regs.
From practical perspective though, as others have mentioned, getting stuff out of an aircraft is usually not as simple as opening a door and dropping it out, you may not get the result you expect!
