For the sake of all that is holy. This would be an amazing feature. Store it in TG cache or something and TG could ask if you want to recover. Sometimes I forget that I haven't even saved a new starting project when just doing something as simple as a material example, just to have TG crash when rearranging object nodes... of all thing (ugh). Seems the backup system is there for saved projects, would seem appropriate to extend that to unsaved projects like other programs.
Oh yeah.. Terragen saves really slow. I suppose the XML builder.