To your point one, I agree. I also fail to see how universal binaries help. The problem isn't with supporting multiple architectures, it's with supporting multiple distributions.
Regarding point two, the developer is stuck with the packaging hassle regardless. The binary goes one place, config files and man pages in others, maybe you want a launcher in the gnome and kde menus... You are stuck with writing an install script anyway.
Yes, universal binaries do not help when it comes to supporting multiple distributions. However I have a problem with the fact that Linux people downright reject the entire idea as being "useless". This same attitude is the reason why inter-distro binary compatibility issues still aren't solved. Whenever someone comes up with a solution for making inter-distro compatible packages or binaries, the same knee-jerk reaction happens.
And yes, the developer must take care of packaging anyway. But that doesn't mean packaging can't be made easier. If I can skip the step "setup a cross compiler for x86_64" then all the better.
Regarding point two, the developer is stuck with the packaging hassle regardless. The binary goes one place, config files and man pages in others, maybe you want a launcher in the gnome and kde menus... You are stuck with writing an install script anyway.