Probably not. A crematorium gets up to 1400 degrees F. I doubt a thick body bag could do that.
I don’t know about you, but I wouldn’t be able to do that to a total stranger, never mind someone I cared about.
TBH, I don’t see why human remains can’t be disposed of the way other garbage is disposed of, through the same garbage processing facilities. Just literally take the deceased to the garbage processing center and chuck them into the shredder along with their old mattress.
When it comes to remains, I don’t consider them to be “my loved one”, that part is gone. I will honor whatever wishes they’ve had before they died, but my own wish will be that my loved ones just quickly get rid of my body at a minimal cost and move on. To remember me, just celebrate what I’ve left behind.
Public health. Corpses are breeding grounds for some very unpleasant pathogens, and you want to protect people from them. People working with the corpses or the machines to process them would be at risk. Back in the days of unregulated burial, it wasn’t uncommon for earthquakes and floods to cause large numbers of shallow burials to erupt. So, public health on a number of levels is a concern.
Emotion. Most people don’t have your attitude towards the deceased, although it’s fair to say that some do. It’s also true that how people think they’ll react may differ from the reality of their reaction when they’re grieving. Most people wouldn’t be comfortable casually disposing of their loved one’s corpses. There are many cultures around death in the world, but few could be thought of as treating the deceased remains casually.
Politics. The first and second reasons combine with cultural and sometimes religious norms and make such a proposal as yours difficult if not impossible politically.
I do agree on the other two points you’ve made. This is one of those things that are fraught with irrationalities and taboos, and have been for millennia.