"For each particular stimulus a cell receives, it will increase...

"For each particular stimulus a cell receives, it will increase the production of a certain type of these components (as well as other components unrelated to the stimulus e.g. housekeeping items) and these exosomes will encapsulate whatever is present in the cytosol, hence the fact that no two are alike"

No evolution builds on what works (a package delivery mechanism of mRNA to the neighbouring cell is just too potentially useful not to have evolved structure to suit function. And cells are more organised than that. There is not just a bunch of stuff bouncing around in the cytosol. Organelles like the Golgi Complex and Endoplasmic Reticulum keep lipid layers between the cytosol and some biological molecules that are synthesized. The synthesized molecules are inside a lipid bi ayer (the walls of the Golgi Complex and ER) inside the cell with the cytosol on the outside. The very nucleotide structures of some synthesized molecules can itself be used to direct those molecules to particular destinations (inside the bilayer and separate from the cytosol). To talk about exosomes (which are such a broad category of different things) is almost pointless (and would result in a discussion more like philosophy than science) - there are clearly going to be many different types of exosomes -because exosome production is clearly a big part of what cells do naturally and different cells have different functions so so too will there exosomes be of different types for their parent cells function. But the reason I'm completely confident that the statement no two exosomes are the same is effectively going to be wrong for all practical purposes is because I know that cells aren't random, they are structured. And so the exosomes of a particular type produced by a cell for a particular purpose are going to the same enough. Structure relates to function.

There is a relatively recent paper (popular science rather than academic journal) Exosome Redux which from memory describes that it is already known that some exosomes do have their contents sorted into them.

You talk of MOA and I understand why because MSB has had to grapple with that from the FDA and Adcomm but Ex1 is not going to have a comparable path to commercialisation as MSB - coming much later it will have the benefit of what the stem cell companies (and other basic researchers) learn about MOAs (mechanisms of action). Eating the stem cells companies lunch (after they spend their money making MOAs clear) is actually Ex1's business plan - that is made clear from their announcements and presentations.