Some would say "build it first let's see".
My reply: how am I sure you will believe when it's built. You may consider it magic or voodoo because it is too advanced for you.
I would like to see that voodoo magic. Heck, if you can create a truly decentralized working forum-like platform, I bet you could even make a few bucks from it. But something tells me that you won't be able to do that. Why? Because you are obviously not an engineer and cannot code. And because the blockchain is not a magic wand that makes everything possible.
And, like Rizzrack said, I actually doubt you really understand what you are talking about and I think you may have some misconceptions about what decentralized applications are. For starters, they are not the same thing as having local copies of online data.
I would recommend the "save page" feature found in many browsers. There's also a convenient print button in many threads.
Ahh, good old KISS principle!
