The ESIC tax concessions appear to only apply to issues of 'equity interests', i.e. ordinary shares. However further ATO guidance indicates that is not entirely true of all equity instruments.
Generically, this means that convertible note or SAFE note investments will not eligible until converted into equity, which is clearly a timing issue, however that does not attend to the question of the issue of those notes themselves could qualify.
For example, does an 'equity-like' converting preference share qualify as an equity interest when it is issued?
If you follow, the rules classifying interests as 'equity' or 'debt' are defined very broadly. i.e. firstly the instrument must not be classified as a debt interest, and thereafter pass the equity test in s974-70(1).
Items 1 through 4 therein outline the logical aspects of equity, i.e.; a right to a return based on economic performance (past, current or future), a return subject to the discretion of the company, an interest in, or an interest that may convert to an interest in the company, etc
whereas debt is loosely classified as 'a 'financing arrangement' where the parties have a non-contingent obligation to provide a financial benefit'.
Further digging shows that "an obligation" is considered non-contingent if it is not contingent on a condition, other than the entities willingness to meet an obligation s374-135(3).
So what does that mean?
Well, It's clear you'll need a tax lawyer to tell how it applies for sure, but from my side, you don't have 'equity' if you preference shares were/are redeemable.
Given the ESIC concessions have a natural cut-off date, it's surely a question worth digging into!