It would be, of course, much appreciated if you communicated with us on the topic, and helped enhance Pango to meet your needs.
You aren't going to internationalization right on your own.
I'm the one to blame for the latest rewrite of the text layout code. Off the top of my head, here are the reasons that Pango Layout was not a suitable solution for Inkscape. I may be mistaken about it's support for some of these items, but when starting out it became clear that Pango Layout did not support all of them.
1) Non-rectangular wrapping (<flowtext> element).
2) Custom kerning attributes on <tspan> elements (x, y, dx, dy and rotate).
3) Vertical text does not seem to be available (although I expect my implementation of this is broken at the moment; it usually is).
4) The SVG spec requires that glyphs are output in logical order, not visual order.
5) Hinting cannot be disabled (I didn't write that bit of the code, so haven't fully explored whether this is true).
6) The list of text styles available is too limited.
Having said that, Pango itself is truly excellent and you are absolutely right that I could not have got anywhere near where I am now without it.
I believe that there is a place for a library supporting advanced text applications, but that Pango Layout is not it. The overhead is really quite large and seems unnecessary for an API whose primary goal is laying out text in widgets.
I look forward to continuing this discussion.
Richard.