Then you still have the mines and two guys behind your lines.
Mines are dealt with easily, either by Operatives spotting them, or tossing nades in high traffic areas. It was common practice to use nades to find mines in previous SD games - after so long, you just knew where to look for them. Besides, even if someone ran through a minefield, it would just clear the way for the rest of the team. The chances that 2 players (him and his friend) would be able to fend off wave after wave of spawning players long enough to actually make a difference, without dying in the process, is slim to none.
The only way I see what he proposed actually working, is if the team as a whole attacked, (or at least a squad) not just 2 players. He may have the right idea, but it is being applied poorly.