I don't believe in imposing fines on those who leave the battle as all it will encourage is just AFKing in the MCC or somewhere on the ground with a rubber band on their controller so that the server won't be able to sense inactivity.

To me, the better option has, and always will be, incentives for completing a match as well as winning.

Jadek Menaheim had an idea in place that utilized the personal warbarge for creating cumulative rewards that stacked more and more with every consecutive match you completed up to a maximum. The more consecutive matches you finished, the bigger the ISK and SP earnings and maybe better chances to getting good salvage. And if you win consecutively, your ISK and SP earnings go up even more. However, your earnings multiplier resets back to normal as soon as you leave a match before it finishes and you will only earn the base amount of ISK you earned for the time spent on that match you left. Jadek's idea takes full advantage of the upgrade features of the personal warbarge.

Another alternative is to introduce a permanent Daily Mission (just like the daily key) that rewards you with a lot of ISK and SP for completing a set number of matches in a row for that day without leaving. Win a set number of matches in a row to maybe earn a key or booster. PC battles would not count towards these particular daily missions but they would count toward pubs and FW.

Make the rewards worth it and you will see players get motivated to finish the fight. Punishment will only encourage them to leave more.

PS: If by any chance someone gets disconnected or gets scottied, a feature should be implemented that allows you to rejoin the last match as long as it is still in progress and as long as you get back in within the next 3 minutes. If you wait longer than that to rejoin, your consecutive multiplier resets to zero and your spot in the roster gets opened up for the next player to join in mid-match. This is so that anyone who gets momentarily disconnected by accident or gets scottied gets a brief chance to get back in without having to get the rest of the squad to leave the battle (if they are in a squad).

But you can only join that last match in progress during those 3 minutes. You can't simply join another match.