I am looking into your use-case.
Your first thread (without initiation fee) has a solution posted that I posted here:
www.joomlapolis.com/forum/255-developer-members-support/243869-taxes-help?start=6#324768
Of course, the texts of the taxes are settings, I have used texts explaining what setting used is.
I will now look into your use-case with the initial fee, and do a test-setting with auto-renewing or manual renewal.
I see several possibilities for integrating the initial fee in the proposed solution in the other thread (e.g. using a different initial plan price, or a negatively-priced promotion valid only on subscription, together with stepped fixed-amount deduction in priority 1 and 3), but I want to do check them, taking into account simplicity, clarity for the customer (and tax offices), and maintainability, before proposing them here soon.