Now that it's on the second week some questions about TakiCHANnel can be answered. Probably the biggest on people's mind is whether or not the previous week's video could still be watched when the new one is up. That looks like a 'no' as the video is up (this time it's A.B.C.-Z with the group quiz) and there is no sign of being able to find the past week's video on the site. And whatever the quiz and gallery were meant to be will be a mystery for now as even the under construction links for those have been taken down.
It seems like TakiCHANnel is not the only special website project for Johnny's as Kanjani8 have one that I believe is tied to their Prologue to Patch videos they've been releasing with their recent singles. The website is called Club ∞ and it looks to be more of a tease than anything else right now as once you access it you can only get 'character' introductions so Kanjani8 fans can try to figure out who is who from the descriptions given. Of course this is all in Japanese but I'm sure the Kanjani8 English fan communities have discussions about this topic and hopefully by the release of Kanjani8's upcoming single LIFE they'll have the answers.