If your team is pushed back to beyond the redline, to where your spawn locations are, the game is over. You will not win. The enemy team has already beaten you. The "solution" to this isn't to force people to leave their safe zone and be slaughtered, the solution is to end the game. If your team loses all of the points, you should have a minute or so to retake one. If you don't, the null cannons should begin firing at a greatly increased rate, so as to end the game expediently. The problem of people fighting from beyond their redline is a problem in that games where the teams are so imbalanced that one team gets pushed all the way back and can't push back out again are allowed to linger on, rather than being ended humanely.

The problem of redline sniping is a problem with sniper rifles. Snipers have no incentive to get closer to the fighting, they're nearly as lethal at 500 m on top of a mountain as they are at 100 m, somewhere on the actual battlefield where you can kill them if your'e a non-sniper. Sniper rifles in general need to be made into weapons that require a bit of skill to use, rather than perfectly accurate hitscan weapons. By adding such features as projectiles that have a travel time to reach their target, and permanent scope sway (mitigated somewhat by skills but never eliminated) the long-distance shots will become significantly more difficult. As such, snipers will be inclined to move in closer to the fighting, so as to get kills more easily. This will help alleviate the issue of redline snipers.

Redline tanks are an issue not unlike that of snipers. Having little reason to budge beyond some high-up vantage point far from the fighting makes "tank sniping" appealing to some. The solution to this, I feel, could be had as an aside from making tanks a deeper sort of vehicle to be involved with. That is to say, by giving tanks (and all vehicles) limited ammunition, and making rearming these vehicles something facilitated by installations and whatever else CCP sees fit, you would make sitting atop a ridge spamming shots all day non-viable, as you'd run out of rounds relatively quickly and need to rearm. It wouldn't solve the issue entirely, but with railguns having minimal splash it's less of a serious issue in the first place, as the other weapons have reduced range.

In any case, the solution to redline issues isn't to force people to leave the redline. The various situations involving use of the redline are all individual problems which demand individual solutions.