Hence the proposal to drop the GTK2 builds instead of adding new ones.
OTOH, compiling the whole stack for GTK 2.24 and GTK 3.0 probably isn't the hardest thing ever, it just needs to be done. And it needs to be done only once we change the minimum required versions or a new Debian version is released (because of dist-upgrade and binary incompatibilities). The rebuilding can probably be solved easily scripted.