I only watched the first couple videos there but... is really 7KP the only thing he has¿ Why doesn't anyone hold that¿ If 7KP is all he has I think we're better off without him.
It was his main tool in DOA2U because it was fast and safe. Same with 8K. 8K was an 11 frame high that was safe and launched on normal hit. Typically, the combo would be 8K (launched), 7KP, 4P+K (fullscreen wind gust). Basically those moves were so good that Tengu could actually get away with just spamming those over an over again and would still win. For the most part, that's why he was broken, as far as I can tell.
In DOA4, 7KP was nerfed (slower and not safe), 4P+K was removed and 8K was nerfed. 8K was now an 18 frame high, that wasn't safe, and no longer launched on normal hit. Typical fighting game devs going way overboard on the nerfing.
Now even though DOA4 Tengu was terrible, he was a lot more interesting in my opinion. He received some new moves and no longer focused on just using the same combo over and over again. However due to how bad he was, he was really more of a shenanigan character to me.
I mostly want Tengu to come back in his DOA4 form because it was a more interesting iteration of him, only I don't want him to suck again. Make his 7KP and 8K better again, just not
as good as they were before and give him general buffs to his frame data (a 15 frame jab is useless and so is an 18 frame high). He also needs a lot more mixups. In a game where you can hold out of everything, you need to have mixup options to keep your opponent guessing. He also needs more mid kicks. If I recall correctly, he only had three; 7K, 3K, and H+K.
It really isn't hard at all to make Tengu a solid character without breaking him. TN is just garbage is all.
EDIT - Here are some DOA4 matches. He's much more interesting to watch here, in my opinion.
And although he's very repetitive in this particular video, it's still a cool one just to show off the dive bomb, which was one of his best tools in DOA4.