I don't have any particular opinion on the best way to do this, but from those comments by the tilix developer, it doesn't seem like the approach taken by vte-n

I don't have any particular opinion on the best way to do this, but from those comments by the tilix developer, it doesn't seem like the approach taken by vte-ng was the right one either. From the VTE maintainer's perspective, adding any additional external symbols can create trouble, because those symbols have to be maintained for the duration of the major version, and they can prevent further refactorings. It's usually not easy to get public API changes into old libraries like this.