Recycle internals (mic+speaker) from Google Home Mini?

[baconator]

Short answer is, no.

See also

Hacking Alexa or Google devices to install Mycroft

The echo dot/home mini had 256mb of RAM, which is rather low to run mycroft on. For budget applications a pi 3 and the google aiy voice kit v1 would be a reasonable approach, though not nearly as pretty or compact. The google mini has a similar two-mic system in it as well.