Now if Data had somehow been taken over by Romulans and the ship on a direct course for the Neutral Zone, Picard would probably have had Geordi, manually cut power to the antimatter containment field and destroy the ship.
And you call my idea overkill? In your scenario they haven't even reached the neutral zone, why not kill Data first and try to save the rest of the crew before you blow up the entire ship.
The donut saucer is a funny image, but you don't have to do that much damage, just enough to blow up decks 1, 2 and parts of 3 and probably 4.
Once the big hole is blown in the ship, there is still the lockout code to deal with. While the ship is at warp it's probably not a good time to shut off the computer and reinstall it's programming. And if the ship were on a direct path to the Romulan Neutral Zone, there is no telling how many Warbirds are waiting for it. Warbirds that may have been traveling for weeks or months to avoid the sensors that monitor the Neutral Zone..
They tried to regain control, they couldn't. Blowing a hole in the ship or shutting off the main computer while at high warp is not a good idea in any event.
So if they are heading towards Romulus, and they have tried to regain control, the only option left to keep the ship out of Romulan hands is to destroy it.