Hello Mario, I see a problem with this and it is how YouTubes algorithm works. With this method you will slowly kill your channel and I can explain you why.
If you want to grow a channel with long format videos your audienence HAS to grow with those videos because YouTube will use your subscribers as a testgroup if they should show people your videos.
So you upload a video -> about half of your subscribers watch it -> YouTube will think "Thats amazing. We will show it to more people." And then they start suggesting your videos next to big channels in your niche.
When you boost up your subscribers with people who don't care about your long term videos you will then publish a videos -> nobody watches it -> it signals YouTube that not even your subscribers watch it, so they won't spread it at all.
Every subscriber that is not there for your actual content, hurts your channel growth.
The second problem I see is that you are technically breaking the law and YouTube might ban you from the platform alltogether. That's not something I would risk honestly.
(Experience: I grew two successful YouTube Channels in compliance with the rules)
Tiia
Tech-Journalist, Content Creator