Finally, I'm building into abba the ability to actually generate its own abbreviation rules on the fly.
If the user so desires, abba can take any given text, perform some word and letter sequence frequency analysis on it (right now very simple), and produce its own set of abbreviation rules with randomly-assigned abbreviation characters to apply to the text in question. The ruleset is treated exactly the same as a ruleset read from a JSON file, so anything that abba can do in one mode, it can do in the other. I think this is quite fun.