That reminded me of Hiraiwa Yoshiyasu’s 1885 proposal to write Japanese using the components of the Ahiru script.

That's the library stamp we used in the old days - featuring a thriving banyan tree. It's based on the design by Thomas
and William Daniell who also designed the Society's iconic elephant emblem!

You're probably already aware of the work of 金水敏, but in case not, you can dl the English translation of his book ヴァーチャル日本語 here hdl.handle.net/11094/67215. See esp. ch. 6. (For a potential historical precursor, also cf. p. 90 in my "Foreign sources" paper linked to here: bsky.app/profile/schr...)

The Guia of 1599 is the Jesuits' earliest (extant) print to involve such a combination (and there are not too many in general). But at least they already had almost a decade of experience printing texts either in Japanese or in Roman script by that time. In any case, the result looks quite lovely. 🤓