how to incorporate such a "straight twist" successfully, without making the story boring because of the straightness of the plot?
Make your character in the second round smart, and the twist preventable if you are smart enough.
Imagine this: Team Dead is infiltrating a high tech complex, all dressed in Ninja black, and they come to the central passage to the main computer. They open the lock and are using some wholly improbable piece of CIA equipment to find the combination and unlock the door, and CLICK-CLACK the door unlocks.
The leader grabs the handle and pulls it open. The technician about to disconnect their improbable equipment sees a dot on the display start blinking, then she yells "Wait!" but it is too late, the leader has opened the door, gas sprays down from hidden nozzles, and Team Dead is dead. The camera focuses on the improbable device, the numbers start turning again, and another combination is shown, before the display flickers and the improbable device dies too, unexpectedly also vulnerable to cyanide gas.
Same villain, different complex, same equipment. Team Bright infiltrates the complex, does all the same stuff, but at the door the technician on the improbable device, Annabelle, watches the numbers spin, then CLICK-CLACK the door is unlocked. Leader man reaches for the door but Annabelle slaps her hand against it, "Five seconds!"
Then the improbable device numbers spin again: CLICK-CLACK from the ceiling, leader man looks up. A green light appears on the improbable device, and Annabelle starts disconnecting it from the lock. "Had to wait to defeat that cyanide backup."
Leader man says, "How did you know that?"
"Lethal locks 403, Harvard Spy College. Oh, but you guys went to Yale!" She winces. "I keep forgetting."
Team Bright proceeds through the doorway and Leader man quickly finds a guard to kill, which makes him feel a tick better about being ribbed by Annabelle.