The idea of Deckard being a replicant opens up a big plot hole

From script to screen, there were many unauthorized changes.
Had the TC come out the way Ridley Scott intended, we would have a quite different film.
Enjoy what you got. Enjoy the other cuts as well.

Impossible is illogical.
Lack of evidence is not proof.
 +  = 

Just how powerful/influential is Tyrell? Are they powerful enough to basically bribe/control the police?


Absolutely. Big multinationals like The Tyrell Corporation will be the largest economic entity this planet has ever seen and they will take over certain governmental departments, like a police force. Just like in the Alien universe where Weyland-Yutani owns the United States Colonial Marine Corps.

1) Yes, Bryant and Gaff know what Deckard is.

2) Tyrell practically owns the city. Everyone works for him to a certain extent. I don't think he needs to BE the government. Not when he can let it be and just throw a few bribes along the way.

3) We don't know if Tyrell's corporation created Deckard or if it was a government black ops division that did. At first I thought that he did, which was why he was so interested in Deckard testing Rachel. But after watching a few times, it doesn't seem that Tyrell pays any special attention to Deckard. It looks as if he doesn't know. Which means he was unknowingly "outclassed" in the "replicant" business.