Ex Kamen Riders' BL pipeline

First of all, I am not an avid Toku fan. I decided to watch Kamen Rider Build after finishing Cherry Magic! and was curious about  Akaso-kun other work. 

I was surprised that I actually enjoyed it. I remember briefly when I was a kid, Kamen Riders were not these "Ikemen" 

Build also had a rather "mature" theme in its story and got me to check the previous and the next series (Kamen Rider Ex-Aid, Zi-Oh, Zero-One) but nothing caught my attention like Build did. Except Ex-Aid but I didn't finish the series. 

I remember thinking when I watched Build, "Inukai-Kun is so pretty he has this 'uke' vibe. I wonder if he would do BL in the future." 

I also had the same thought when I watched Toshiki Seto in Ex-aid. 

I was pretty surprised that my prediction came true years later. 

Now there are questions in my head.

1) How's these Kamen Riders got picked as the lead? Why there has been shifting to more "Ikemen-look" actor? My bet is they want to reach a wider audience, a franchise that was once for boys only, now can gain traction and allure girls viewers. 

2) If they play NSFW BL, would they have a problem with their younger audience? I was thinking about Disney actors and actresses. 

3) what is the entertainment business climate in Japan now? is BL on the rise? what's the difference from the previous one? 

4) For those who have knowledge of the industry, what happened between agencies when their actors played in drama? Is there any fans service culture like Thai do?

5) Any sources, thread links that talk about this topic?