Usually when a vice needs to be locked down its in a place where it will be for the duration of a job. When this is the case I usually just sink a few sleeve anchors into the floor through the leg holes. This also allows a place to chain other equipment at the end of a shift.
On one job in a large food proceesing facility where 80% of the pipe was threaded stainless steel and the work was throughout the plant then bracing the vice was the only way to secure it. The special epoxy on the floor was off limits to any drilling.
Work hard, Play hard, Sleep easy.