I had a different take on this - it's somewhat inspired by collections.namedtuple but mutable and has some other convenient features for data classes: https://gist.github.com/tomstrummer/8240282

(see the examples at the bottom of the file)

This could also be tweaked to use __dict__ instead of __slots__ so it can act as an expando class which I believe is more similar to what the OP achieves.