For one thing, this can't be done without a mouse to drag-and-drop with. This limits the extension of off-store extensions to those who can use a mouse, which is an accessibility issue. Are handicapped users or keyboard-only users just thrown to the wayside these days?

I was specifically asking about jonknee's use case, I never claimed that this would be an ideal solution for every other possible scenario. That said, your request to have a mouse-free way to install extensions is totally sensible, and I would be surprised and disappointed if they did not think of alternate ways to do that (perhaps using the command-line).

I guess we will find out, that sounds like a pretty big roadblock for the skill level of users I am working with.

There seem like there's a better solution out there, at leat for my use case. I serve the crx bundle from the same domain that it interacts with, that seems like it could be pretty malware proof.