OF 
I created recipes for gmime and balsa (albit without icon (no svg is supplied in the source)).
gmime builds and packages fine without patching, for balsa I used patches from Debian and Gentoo, not using webkit2gtk (can’t make configure seem to pick it up, there is still meson that I haven’t checked out).
I you don’t mind I can push those to haikuports (haven’t been able to connect to my gmail account, but I also haven’t used any email app on Haiku so far).
Not sure if you had any other patching aside for build errors done on your side?