No. There are so many buggy, non-fsyncing programs out there that, if a filesystem has 1G of writes outstanding, it's almost certainly going to lose many hours of work. (Unless it's manually flushing every 20 seconds or so, in which case that's fine but also slower than tmpfs).
In an ideal world, you're exactly right. In today's world, that would be fairly dangerous.
> I've seen filesystems that have mount options and file attributes that specifically indicate that files are temporary
Agreed, but if you're remounting part of your hierarchy with crazy mount options, why not just use tmpfs?