It would turn into a game of defending your opponents goal to prevent them from scoring on themselves. Actually if you think about it, it could add a whole new element to the game and maybe even be exciting, if not more confusing...
This would mean that a team attempting the "suicide" strategy from the outset would need to be much better in that paradigm than the other team. If we assume that the skills involved are similar, this would mean that they could probably win anyway using the normal rules. Adopting the strategy partway through the game -- say, when behind by three goals -- could be effective, but if the other team knows about this, they would keep the difference to only two goals.
It would result in either a heavy emphasis on defense, or a strategy of scoring one goal and then passing the ball around for the rest of the game.
Since different teams get the initial and half-time kick-offs, it boils down to which team is capable of scoring the most own-goals in the same (lengthy) amount of time. The second team has a huge advantage, because they win by scoring 4 less own-goals than the leading team.