whoami | /mnt/us/extensions/espeak/espeak.sh
works from kterm (gives the voice output "root") - but I'm afraid packaging that as a kindlet (.azw2) is above my skill level.
(I could learn, but when the initial barrier to entry is "not enough diskspace to install XCode on this Mac" I guess, I might resort to not setting up a dev environment...
)
At least I've given you some tester feedback, if it turns out that more people are having this issue.