3 eng. ferry
On a 3 engine ferry, there is no V1. If you haven't rotated, you abort. Yes, you may very well go off the end. There is no such thing as "balanced field". We do, however, make some computations that are not used in line operations.
Wmc and W1 are calculated. (Yes, those are "W"s.) Where Wmc is a weight that assures min. control speeds, and W1 is a field length limiting weight. If W1 is less than Wmc, we can't go.