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.
Is that a serious question? Blow a big hole in the Enterprise and kill a highly-valued crewman when the ship is in no immediate danger (and, in fact, was never in danger at all)?
Screw the highly valued crewman, even if he's Data, if he kidnaps the ship, looks everyone else out and goes on a mission to do god knows what his death is acceptable after all other options failed.
That the ship was never in any danger at all is irrelevant, you only know that after the fact so it cannot factor into the decision what to do.
Any captain who would even consider that shouldn't be in command of anything but a garbage scow.
I could say the same thing about a captain who twiddles his thumps and takes the wait and see approach while his armed to the the teeth ship is under the control of a single person who apparently snapped or his under the control of an outside person and refuses to even talk to anyone.
Who cares about the locked out computer, that's just a minor inconvenience. After the bridge is destroyed unplug the computer and shut down the warp drive manually. Then try to get rid of the lock out somehow, worst case scenario, delete everything and reinstall, that's what they did when they caught the iconian computer virus, so we know it's possible.