Hope you were being serious when you said anyone is welcome to improve on this!
I didn't "improve" on it as such, I was just getting a few errors with your module as it was with regards to first and last names which have spaces in, so corrected that.
Also switched to API v1.3 (that was hard work, had to change a whole number )
Anyways, my changed file is attached here!
Seems to be working great again, thank you for a great module!
mailchimpsubscribe.zip