They went Avengers: Age of Ultron approach which I didn't like either.
It's kinda strange to see regular human like Black Widow and Hawkeye could beat so may Ultron with ease.

I guess so, but honestly, it gave me a bit Terminator-vibes. I hope they capture that mid-'80s campy pre-apocalypse vibe.
I don't doubt him, he already took many roles as villains afterall.

While he mostly done comedy movies, he can still achieve a wide range of acting.
Girlboss thing is somehow sounds like more Sally than Amy.
Are we sure the movie director and producers didn't confuse the characters?

I think fans, or at least "just me" am worried that when it comes to Amy Rose, there is two possible outcomes.
1. They make Amy like how she was in the early games, in which there will be backlash from feminists who think Amy should be a strong and Independent woman because political and progressive ideals.
2. They make Amy a strong independent woman to the point she is a degree Mary Sue and Sonic fans will complain she's making the main characters look pathetic.
https://www.youtube.com/watch?v=nygfvI5cZ9wthey'd rather have Amy meet in the middle. Be an asset to the team and at least have some insecuriities or challenges to overcome than pandering to make her this perfect heroic figure to put Sonic asside for.
There's also a possibility for a totally new enemy but I'd prefer if they're from the games (unlike Knuckles TV series).
there is. But there are some slim pickings that I doubt Sega/Paramount will choose, such as Mephiles or Infinite. And making a brand-new villain such as The Buyer would be a risky move, especially given the Buyer didn't do much.
Just because he's back doesn't mean he's still alive.
It could be flashback scenes or ... yeah ... dark alternate future scenes where he won and rule the world with the army of Metal Sonic.

I know, it's just, the third movie had more emphasis of Dr. Robotnik's death than the second movie.
Don't get me wrong, as long as Jim Carrey wants to continue the role of Dr. Robotnik then Sega/Paramount should make the most of him.
But at the same time, we had Dr. Robotnik as the main villain for three movies now, so why not give the main villain role to someone else for a change?
I know you said you don't like the Ultron approach, but why not Neo Metal Sonic with an army of Metal Sonics? Way I see it, it can be more like Terminator in vibes. A fun somewhat campy mid-80s action film.