I watched "DownTown Now", a Japanese TV talk show briefly. Kajisakku, a former TV comedian and now a YouTuber with more than 1 million subscribers, suggested YouTube contents ideas to DownTown, one of the most popular comedy duo, and Shinobu Sakagami if they become YouTubers.
These days many Japanese TV celebrities start their YouTube channels but it is really up to the contents if the channel becomes popular ot not. Just being famous is not enough factor to get subscribers.
坂上 ー 夜のバイキング(昼の番組で言えないことを言いたい放題で言う)、番組の反省会の模様
松本 ー 一人ごっつ、筋トレ動画(誰か他の人に撮ってもらう)
浜田 ー サバ定食を食べる(誰か他の人に撮ってもらう)
Sakagami - Night "Biking" (he hosts a tv talk show called "Biking" at noon. He discloses what he can't say on tv). Or the tv program's staff meeting.
Matsumoto - Hitori-Gottsu (a solo comedy show he used to do on tv). Muscle exercising (he is very muscular. Shot by someone else).
Hamada - Eating Saba (mackerel) meal alone (shot by someone else).
- 内容にすぐ入る (挨拶やチャンネルジングル？は要らない)
These days, I think those are the good contents to start YouTube:
- Things you have already been doing
- Start the contents directly (no need to greet or channel jingles)
- Things you don't make any efforts to do (laughs)