(realized that the author doesn't see itch ratings, so reposting here from a long time ago)
The idea is gold; well worth the $5. The document, however, is not.
If you are someone who is looking for inspiration for your own roleplaying game or are willing to do some hacking yourself, this product is for you. Full stop. However, if you're looking for concrete rules to port into your OSR game, you will be disappointed.
Because I'm the former, this is a positive review. While I won't reveal the idea (as that is effectively the document besides an example and some suggestions), it is certainly a great one that I'll be sure to use in my own hack. There are a few minor concerns I had in my read-through.
Until I read the example, I thought what defined a "rule" was more like "roll a d20 when you attack" and less like "as a Cleric you have Turn Undead". Could've been a bit more clear in that regard. Secondly, the document doesn't have enough confidence in itself. While I understand the desire to make sure that readers understand that the legacies might not be to their liking, curbing disappointment somewhat, I found that it had the opposite effect on me and effectively curbed my excitement towards the legacies.
At three spots in the five page document the author basically says "hey, this is a proof-of-concept, so take what I'm saying with a grain of salt!" So, I took my excitement with the grain of salt requested. Ultimately minor complaints, but still complaints that somewhat held back my otherwise great read and food for thought.
Would recommend.