Making battles more competitive: motivation to win

P2W is not the only revenue model. They could make every weapon and bot available with Ag and wsp and reserve Au for cosmetics only. 

ionflow - Which they also have for ridiculously expensive Skins

...or in less words they go defensive. Its a natural response to stronger opponents. And as for the players only seeking max damage...Max damage and beacons need to be done for a win. The more of both the better...Maximum damage is in no way a bad thing.

You seem to think that once the point in a game comes when the other team has dominance that teammates trying to do max damage hurts the effort?? I have seen enough games lost on the bar only to be won on the mechout thanks to max damage.

Perhaps you missed this part: "P2W is not the only revenue model"

There are games making more money than Pix could ever dream of that have zero performance enhancing items for sale. Ever hear of League of Legends? Google it some time.

If you want to make the game more competitive all you have to do is change the distribution of league points. I ran 4 games earlier and won 2. All games I had around 350-375k damage (top was around 500-550k) and got 4 beacons one game, 3 beacons in 2, and 2 in the other. I did my part to help the team. The rest of my team and most of the reds just stayed firing at range most of the match. Why? Because in 4 matches playing to win I lost a net of 24 league points.
Everybody is more concerned about being the bottom 3 on the losing team and losing 10-20 league points then they are concerned about getting beacons and winning matches. If you make it so that the bottom preformer on damage doesn't get 「grape」 on league points, people wouldn't be as afraid to lose a few damage points so that they can cap a beacon and help the team actually win.

Edit: this would also have the side effect of making it harder for people who just stand there to drop league points for taking purposes.

Fundamentally, this idea isn't too different than mine (OP), a combination might work and reduce the number of people tanking. Lower the league points penalty, but still have the losing team placement be determined by caps not damage. 

At about the 4 minute mark of a match any player should realize they are on a losing team (if that's the case); well they have even greater incentive to cap beacons, because they know their end-game placement will most likely be determined by caps not damage. Take some beacons and they might surprise themselves, and if they do win their placement is then determined by damage. 

My original arbitrary au reward for the top losers was just what would motivate me to cap more on a losing team. If it doesn't motivate anyone else then find something that does, because in my opinion capping is just as important as damage in a good competitive game. I just hate seeing losing blues just go for damage, and you have to grind out the long defeat with them because no one is trying.

Won't change that there is a strong incentive to tank: You get easier matches if you finish with -20 points.
The matchmaking is the problem here, in that it gives value to losing. This has to change. (Which I will write here seemingly 10 times a day for a long time.)

"Oh great, now I get an even bigger penalty for trying to turn a lost game. If you're already above your fair league rating, any more league points you earn push you towards a higher league, where you'll be even more outmatched."

I thought this too for a long while. However we already have this problem, I am sure you have a had matches where you get opponents or teammates from a league up or down from yours. The issue is that for you to get the points to move up the have to come into the system all the way FROM THE BOTTOM. This is an issue with ELO (what leagues are like) and even it has to inject points every now and again. Right now this motion of points is somewhat random (MM might know very well what it is doing with these matches) but it already happens, at least this way it is transparent. 

As for clubbing incentive for leagues is pretty large, but it is distributed "up front" rather than on the daily. Apirl first will pay you out for your league, but you won't see league  gold again till May. This means you can collect your league level gold all on april 1, tank down and stay down till the end of may and THEN battle your way back up. With the above changes to how gold is distributed (all winners get gold equal rather than an outsized portion to the top) and league gold daily rather than "up front" you would see people invented to STAY in their league as the payouts are more balanced.