If you start a private forum, this has the disadvantage that it would put up a barrier to people could make use of the valuable information. A public forum would need to be carefully curated to avoid having it drowned out by the clueless majority. Both would need to attract an audience.
HN has the audience and is close to what you want, but the problem is that thoughtful discussion is drowned out by the sea of clueless groupthink. Someone who wants to contribute to the thoughtful discussion has to read, evaluate, and deliberately not respond to the "you're so wrong" comments.
But suppose I could highlight the thoughtful responses, and share that with anyone who wanted to see the thread through that filter. Now anyone can see just the posting and the thoughtful responses, if they want to. And it's a lot less work for them to join in a thoughtful discussion, because they don't have to plow through the clueless majority opinions.
Next, imagine you could create a group, such as "successful entrepreneurs" which would be able to share responsibility for maintaining your filter (instead of just one person having to do it). You would be in charge of membership of a group you created. Now anyone in your group could mark a post or comment as being thoughtful (or interesting or useful) from a "successful entrepreneur" perspective. And if I was interested in that perspective, I could choose to view HN through that lens.
This would also solve the problem of good content quickly falling off the front page. Everything that had been selected by your successful entrepreneur group would remain available in the lens archive.