- Splitting into fixed size chunks: 2-3x
- Ring signatures with a sane minimum for guaranteeing anonymity: 3x
- Block time: Negligible in the limit as the number of transactions increases
- Bigger individual signatures and addresses: 2x
Mostly agree, but one comment. Ring signatures do not make up the entire block chain, so using a mix factor of three (approximately 3x signature size) does not mean 3x in terms of blockchain size factors. Perhaps you are already assuming a mix factor of 5 or something, and the 3x number includes this.