support languages of Vanuatu, which are currently very difficult to typeset, with no text flow
AFAICT, InCopy (and InDesign) do not currently support several writing systems, which makes font design for those scripts difficult. The avoiuli script of Vanuatu, for example, which is boustrophedon and can change from btm-to-top to top-to-btm. I'm working with a professional typographer, and trying to design a font that can't be implemented by any word processor that we know of means that a lot of choices in the design are probably not optimal. The best option currently seems to be placing a hard return at the end of each line, with manual RTL/LTR control, and sorting the lines in reverse in many cases. That messes with text flow and makes InCopy/InDesign essentially useless for publication. It's actually easier to typeset in a spreadsheet! (That lets you sort by line number, whereas in InCopy, in order to rearrange the text one needs to cut and paste each line of text individually.)
Feel free to contact me about requirements, but basically we need boustrophedon support. Texts may start LTR or RTL, and may proceed bottom-to-top or top-to-bottom. Formal text direction is RTL bottom-to-top, but under Latin influence LTR top-to-bottom is usual in informal texts -- though still boustrophedon. Glyphs flip direction (mirror-image) when the line direction changes, though of course that could be handled by the font. It's also a linking script, which needs to be kept in mind when changing direction.
I don't expect much from MS Word, and LibreOffice is volunteer-run and does not have the resources for minority-language support. It would be nice if an elite product like InCopy could provide support to unsupported languages. MW and others might then follow suite.