IMO a realistic fourth (or more) option that has warships in RAN service by 2030 is a bit of a unicorn.
An in service date by the end of 2030 is only ~7.5 years away.
In order to complete builders and acceptance trials, construction and fitout would likely need to be finished by ~6.5 years from now, or possibly even earlier likely only 5.5 years from now.
If the ship build went well, it might only take ~24 months, though lead ships, particularly of new designs often take a bit longer. What this means is that first steel cutting would likely need to be started NLT ~4.5 years from now and ~2.5 years from now would probably be a more realistic requirement.
In order for steel to be cut, orders would need to be placed and the detailed design work would need to be finished. Those processes typically take about two years though they are sometimes a little shorter and can often be longer. These would likely need to be done NLT than 2.5 years from now, and IMO within the next six months would be a more likely requirement.
This is also where it should start to become apparent that there is a time crunch problem. If detailed design work needs to be completed within six months as well as orders placed and contracts signed, then several processes involved in ordering new warships would need to have already been completed.
In order to get a detailed design, then the base design and design would need to have already been selected, as well as what the systems and armament fitout would be. Long lead items would also likely need to have been ordered either whilst the detailed design work is being done, or before it even begins for some of the really long lead items. These types of timeframes can take a couple of years, so this might have needed to happen last year or possibly even back in 2020 or earlier.
In order for a base design to get selected, there would need to have been consideration of what the RAN would require in a new warship class, what characteristics, what capabilities, how many, etc. This would likely have added yet another year or more to the actual start date in order to get something into service by 2030. So now we are looking at a process which would need to started by around mid-2021 if not earlier.
Instead, there has been a DSR which is to be followed by a naval review. That naval review might very well be what Australia would need to have done to kick start the processes to make a selection on design requirements and fitout. The problem with this of course is that something like it would need to have happened at least a few years back in order to achieve an in-service data of 2030.
Consider looking again at the RN's Type 31 programme which
@alexsa mentioned earlier. The expectation is that the lead ship will be in service by 2027, after being launched in 2023. That expected launch date comes after being laid down in 2022 whilst first steel was cut in Sept. 2021. The cutting of first steel (at an active yard with a skilled workforce) comes about two years after the design was selected in Sept. 2019. That design competition itself started around 2017 and that came after the 2015 SDSR where it was determined that more GP frigates of a lighter and more affordable design than the initially planned number of Type 26 frigates would be ordered.
In short, the expectation is that it will have taken about a dozen years between when the idea of the Type 31 first came up, to lead ship in RN service. Applying that same sort of timeline to the RAN now, with the DSR and naval review being equivalent to the 2015 SDSR, would see the lead ship in service by 2035.
This is what I do not think there really are any realistic options to get new warships into RAN service by 2030.