a "Suicide-burn" landing autopilot option. - calculates its wheight and it's available thrust, and then tries to burn at max capacity at the latest possible moment

Normally, the landing autopilot will often just maintain a steady decent speed by firing the engines multiple times during landing. Though if you are short on fuel this might be a wastefull method that doesnt carry a lot of risk.

The suicide burn would be the result of burning at maximum throttle just before impact with the planet surface.
Optional would be to set the "contact speed", the speed that the rocket has the moment the rocket touches the surface.
Even though this would be a risky approach to landing, it would be usefull as a last resort.

A tickbox with "Use all fuel" could be used for situations where fuel reserves are insufficient to land properly but might be enough to touch down with a survivable speed. (especially if it's a powered decent into water) This option would give you your best bet at surviving impact

To assure players of the system active i would suggest a display of the "burn altitude" or "countdown to burn" that show's the predicted moment of the suicide burn.