The non-snipers who have been redlined are redlined because they've lost the game. They've been pushed back from all spawns and now they're being farmed by the enemy team. The "solution" to the issue of redlining isn't to make the people who've lost and are being farmed now get 50%, or 0%, or any value less WP than they were previously getting. The solution is to make fighting from the red line not something anyone ever has to do.

To that end, first off, when you've lost all objectives the null cannons should go into overdrive and greatly accelerate the damage they do to your MCC. In other words, when you've lost the game by being totally pushed back, you should have either a brief time to salvage the situation and take an objective (and therefore spawn point) beyond your redline, or the game should end. Protracted fighting of people behind the red line should never occur.

Second, sniper rifles are an obviously broken part of Dust and need to be fixed, period, irrespective of redline sniping. People using sniper rifles so far from the fighting that they are shooting from the redline should be essentially ineffective. Sniper rifle shots need to have travel time, bullet drop, and the scope should always be swaying. Snipers shooting from their redline should be so impaired by shooting at extreme ranges due to the aforementioned sniper rifle mechanisms making it very hard to hit distant targets that they simply don't ever do it. Bring snipers in from the 500 m mark, make them an actual part of the fight rather than tiny specks in the distance farming kills, and the issue of redline sniping will be gone.