That's an excellent idea. In the past, "partworks" were common, especially in Europe. But it is probably outmoded.
The best way to publish this type of work is with an "on demand" system in which an update every 2 years is relatively easy. "On demand" means books are printed as and when needed in short runs. Quite possibly, this style of publishing gives better revenue for the author. However, it would be up to the author to organize the updates etc.