Gender neutrality when quoting English originals and translations?

I have read most of the gender neutrality threads on this forum and googled but failed to find detailed proposals on one aspect of gender neutrality: using it when QUOTING sources written originally in English and especially English translations from other languages. Plenty of discussions how to use it when writing the original text in English or when translating but not when QUOTING.

I have identified myself four ‘levels’ of gender neutrality to be used in different situations of quoting. I would appreciate your comments – which levels you accept (do not accept) and why.

Level 1. Modifying the English quotation when the text in the original language is gender neutral.
For instance, there is an actual translation ‘Man is a creature whose will is greater than his ability” (from German “der Mensch ist dasjenige Geschöpf, das mehr will, als es kann’).

I have no doubts about modifying the quote to a neutral one, with square brackets in relevant places to show that this has been done.

Level 2. Modifying the English quotation when the text in the original language is NOT gender neutral.

For instance, there is an actual translation “Man only exists insofar as he expresses himself” (from German “Der Mensch kann nicht anders existieren als indem er sich ausdrückt.”).
I think it should be fine changing the English quotation to make it neutral (e.g. ‘[Hu]man only exists insofar as [they express themselves]). Same if the source of the quote were originally written in English.

Level 3
Changing the translated or original title of a CHAPTER in a book or the title of an ARTICLE.

For instance, a chapter in a book is translated as follows: ‘The Spiritual Problem of Modern Man’. In the footnote containing a reference to this source I would like to modify the title as follows:
Carl G. Jung, ‘The Spiritual Problem of Modern [Hu]man,’ in The Collected Works of C. G. Jung.

Level 4
Changing the TITLE of the book that is quoted.

When providing a quote from the book published originally in English as ‘Man and His Symbols’, the footnote would read

Carl G. Jung, ed., [Hu]man and [Their] Symbols

The practical problem is that, at this level of modification, it might be difficult for the reader to find the book if needed. On the other hand, the title of the book was supposed to be gender neutral originally and the modification does convey the true meaning.