5e The Flee Action and Pursue Action: a Solution to so many issues (I think)

[BerzerkerUnit]

Here goes: I think this might be a solution to Player created traps (like how they can actually employ them).

You're running a combat, an enemy flees. They're defeated, you want the PCs to focus their attention (if not their fire) on the remaining foes, but someone wants to keep shooting at them. THEY'RE NOT A THREAT you want to shout, but there's cover, range, someone wants to give chase it's just a meaningless exercise of attrition. It might be tactically sound, they don't want someone to get reinforcements, but it's usually a little more... I don't know, spiteful? Or even metagamey. Like if you kill a goblin raiding party and one or two flee, it may be years of ingame time before they could successfully mount a quest for revenge as a group. Finding a way to feed their clan is probably the more pressing matter for the next generation. A lone goblin would have to undergo years of training to become a threat on their own or quest to get contacts to track you down.

Introduce the Flee Action.

Flee Action: You can take the Flee action to escape a combat. To take this action you must have no enemies within 30 feet of you and must have a move speed greater than 0. Once a creature has fled it is not targetable with attacks or spells. It may be caught in areas of effect that target other creatures (so fleeing through your allies is hazardous) but has advantage on saves.

A creature that flees cannot rejoin the current combat. Flight of this nature is intended to move to a place where they can regroup to hide, complete a short or long rest, or initiate a counter offensive on more advantageous terrain.

Pursue Action: When you see a creature flee you can take the Pursue action on your next turn, provided you have no enemies within 30 feet you and your move speed is greater than 0. Pursuing a fleeing creature causes you to exit the current combat and initiates a skill challenge with the fleeing creature.
The Fleeing creature and Pursuer make a series of opposed checks. The fleeing creature can use Athletics, Acrobatics, or Stealth to escape and pursuers can use Athletics, Acrobatics, or Survival/Investigation to pursue. The DM should impose advantage or disadvantage on either side due to factors such as familiarity with the terrain, hazards, weather, or other appropriate phenomena. The first side to gain 3 successes can determine the location where they engage again. New initiative should be rolled and combat will begin as normal. The losing side gains a level of exhaustion that can be removed with a short rest.
A Pursuer that loses an opposed check by 5 or more loses the trail entirely and the fleeing creature or creatures can move to a location of their choosing and complete a short rest.
A Pursuer that wins the opposed check by 5 or more can choose to drive their quarry to a location of their choosing and engage the target again.

Voluntarily abandoning a pursuit early is considered a failure and result in exhaustion as normal. Circumstances such as impassable terrain may allow quarry to escape, such as a dragon flying over a massive canyon, but this is not considered a failure. At the DM's discretion a pursuit may end prematurely if there's a chance the quarry or pursuers could have a random encounter such as a hostile patrol, potential hostages, etc. This is considered a draw and does not incur exhaustion.
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How does this work in combat. Just like it says, but their are strategic implications.

The Rogue scouts ahead, biffs it or maybe murders a lookout and then wants to bug out. No more painfully dull mathing out how fast the rogue is with double dashing and can it escape compared to pursuers. Now they can just skedaddle back to the party, possibly even luring the enemy into the area where the party has prepared Traps! or an ambush. But also, they risk being cornered, and continuously fleeing is a poor option due to the exhaustion mechanic at play making it harder and harder.

Now your NPCs and monsters can be run to ground. Why doesn't the dragon just fly away? Now it can, and the party can follow. Successful pursuits can start to stack exhaustion on the bads. This makes Rangers and Rogues amazing as a means of driving or luring quarry into party set ambushes and trap zones.

My PCs are just starting a campaign where a consistently available mission type is Pacification of some deadly creature and this feels like it's going to create some awesome opportunities to run those down.

[JNAProductions]

The party engages a horde, in two ranks. The front rank has shields and spears, the back rank has shortbows and the boss. The boss wins initiative over everyone but the party's Fighter, who's a Sharpshooter Samurai.

The Samurai peppers the boss with a bunch of arrows, but because the boss has loads of HP, they survive. They are, however, scared, and so Flee the combat. They use a Bonus Action to Dash away, and end their turn 60' behind the second line of enemies.
Up next is the Wizard. They cast Firebolt or Scorching Ray or something else at the boss. But they can't... Why not?

I won't say it's bad for its intended purpose, but it's REALLY gamey. No one in the party can Pursue since there's a front rank of enemies, but the boss is now immune to everything for purely metagame reasons.

[BerzerkerUnit]

The party engages a horde, in two ranks. The front rank has shields and spears, the back rank has shortbows and the boss. The boss wins initiative over everyone but the party's Fighter, who's a Sharpshooter Samurai.

The Samurai peppers the boss with a bunch of arrows, but because the boss has loads of HP, they survive. They are, however, scared, and so Flee the combat. They use a Bonus Action to Dash away, and end their turn 60' behind the second line of enemies.
Up next is the Wizard. They cast Firebolt or Scorching Ray or something else at the boss. But they can't... Why not?

I won't say it's bad for its intended purpose, but it's REALLY gamey. No one in the party can Pursue since there's a front rank of enemies, but the boss is now immune to everything for purely metagame reasons.

1st, the boss’ flee as described isn’t viable. The purpose of flight is to exit combat to regroup. At a minimum you’d be running until you were no longer able to see your foes.

Maybe it’s more clear if I use XP as an Example.

If a foe flees from combat, you get the XP for defeating them. They are no longer a threat. They could comeback, but they’d have had a short rest at least unless someone pursued them. But the idea is if they fled far enough to avoid pursuit, you’d have a chance to rest before they could return.

Still within range of the archer you’re trying to escape would be disengage or dash.

Fleeing back into your fortress or burrow filled with traps would be reasonable, fleeing from the foyer of castle Ravenloft to your crypt or tower top roof would be reasonable.

Given the rules I posted that flight could go as follows. The boss flees, the party pursues, skill challenge, maybe the party is led into another encounter full of foes, maybe they can force the boss into a room with no other exits far from his allies. Maybe they lose him altogether and will encounter him at another time.

It’s an action option designed for players and smart foes and foes that can be defeated by driving them off. Wolves forced to flee from a well defended farm are likely to just steer clear thereafter unless it’s the only source of food in a dying land.