Battle Royale games are slowly encroaching on PS2's niche. PS2 needs to take lessons from them.

As a dedicated LA and someone who flanks every opportunity I get in vehicles, I think the risk/reward would be too off-balance. Currently all the accidental discoveries and running into too much to handle is acceptable because my death means relatively little, and the eventual success can be much more rewarding as it gains me the ground my team needs to progress.
But if every failed attempt gets heavily punished with a higher death penalty, that playstyle becomes terrible to try and maintain and likely punish the user more than the enemies you flank. Why waste all that time and effort if you could be better off using a HA and trying to get a Lucky entrance at a side-door and mow down a bunch of people.
But ultimately, I think that a lower TTK would benefit the zerg more with easier murder of anyone Who opposes them.

Adding in an optional Battle Royal mode could fragment the PS2 population to such an extent the game would die. Changing the game to be mandatory battle royale would kind of be like reinventing the wheel for Daybreak since Daybreak already owns one of the most successful battle royale games: H1Z1.

I have no problem with battle royal games. I think you are right that looking at the success of battle royal games may be warranted. But, ultimately, if I wanted to play PUBG I'd play PUBG. If I wanted to play PS2 I'd play PS2.

Everything that is the PlanetSide franchise: spend millions in ongoing development, start with unequaled potential, and then progressively tune the game to be more unplayable and obsolete for 99.999833% of the world's gaming population?

It's tradition.

Touche.

The things they could do with "Battle Islands" boggles the mind.

is that 2017 slang for incompetence?

incompetence is unintentional.
tradition is mindboggingly dumb repetition that should have been fixed after the first time.

Anyone who thinks flanking in PS2 isn't effective probably doesn't know how to flank, or how to properly exploit a successful flank.

The easiest example to give is the difference between fighting in a meatgrinder for 20 minutes or flanking, taking out the enemy sundies and ending the battle in seconds.
Getting behind the line of heavies to take out the medics, collapsing the line.
Getting access to an MBT's rear armor.
Etc...

We don't need more lethal weapons, flanking is already very rewarding.