I promise this is a serious suggestion and not snark, but I respect projects that resist adding poor implementations of other applications' core functionality. Type rendering is hard! Let GIMP be an excellent RGB-pixel-pushing program, and maybe give a real page layout application a shot instead. The output will be worlds prettier than anything you'd be able to do in GIMP. Scribus is nice: https://en.wikipedia.org/wiki/Scribus

Scribus is great for layout, I'd use Inkscape for text around a curve and then import it.

I've always wished for a common canvas so one could attach a program to a canvas - eg in a new layer - and add parts, rather than passing files around.