I'm in the same boat, though I do at least have direct finance arranged as backup.
It's worth exploring other options to hedge the risk the bill doesn't pass or a M3 becomes ineligible when it does. I've done my own calcs and personally it still works out a good deal to start on finance and then break it after a few months then do a sale and leaseback to get into a novated lease. There is an extra cost of doing so vs just trusting the legislation will pass, but if you go with a lease and it doesn't that's going to cost more than a direct finance.
The difference between an immediate 0% FBT Novated Lease, and the option above to delay starting one after delivery is less than the cost of the acceleration boost (and that includes the lost GST savings, break costs, fee estimates etc.). If the bill doesn't pass or is changed then it could cost me over 5k more to do a Novated lease vs direct finance and I would be much more locked in.
As always, this is specific to my circumstances. If you don't know enough to do your own calculations then engage a tax accountant or financial advisor.