Here are some of the elements that would make it more compelling.
* Provide a reference implementation in a widely-used language. I would pick C or Rust. The code should be under a widely used open source license, have high test coverage, and be fuzzed.
* Write a specification and conformance tests. What happens when a word is not in the dictionary or the dictionary is corrupt?
* Provide size and performance benchmarks of real-world datasets. You assert that English words can be encoded compactly so try encoding Wikipedia, Project Gutenberg books, or the text files in the Calgary Corpus.
* Compare your proposal against state of the art compression algorithms like PPM or LZMA.
* Fork a text editor application and change it to use your reference implementation. What are the effects on editing latency and RAM usage?
* Shared dictionaries were tried in the 1980s (e.g. Spellswell Word Services) but failed in the marketplace. What's different now?