I don't know whether you have this kind of a script in the game already, but if there are certain things you want people to know about the hack (engine hacks, moveset changes and such) before they start playing, have you considered building the information in the game?
Have a book or a thing similar to that in the main player's room. With multichoice options, you can choose the topic you want to read about and the book covers all the information about the hack you want to share. This would also solve the problem for those getting the hack elsewhere (most people gets these hacks from "less legal" sources, whether we want it or not).
Of course, README is there for stating people to read it. But still, probably less than 5% of people really do that, and I'm actually no exception (tend to check readme only if I have problems with getting the wanted thing to work).
So yeah, just a piece of advice. Do as you like, I personally will include this kind of a "feature" in my own hack.