Hmm, your answers are enlightening. On the first and second point, it seems plausible that such diverse toxins could exist, provided that toxins refer to anything that damages the host DNA/RNA. I take it that you meant bacterial virulence can be toxins as well.

The third point makes sense as well, that individuals not exposed to the secreted exosomes could then secrete their own. whether the exosomes becomes corrupted and turns pathogenic would explain who would become symptomatic.

The concept of our immune system making the virus/exosome and secreting into the environment could very well be another hypothesis on the origin of viruses/exosomes. I mean, as you have mentioned, scientists have not even pinpointed how viruses originate.

Still, it’s a difficult theory to experiment with the core question being, what is the specific environmental toxin? But again, it’s not like other theories of the origin of viruses can be proven, as far as I know.

I think you could certainly email some renowned scientists in the field of exosomes research. Though I think those professors would think you are approaching them with a PhD research proposal. But who knows, maybe you could help them conceptualized a review/opinion/theory academic paper?