These are just ideas; they have not been implemented into the game.
Two features- NPC Training and Pokemon Selection
The whole idea behind these two features are to make it possible to get some stuff no matter what trainer level you are, without depending on hitdown. In my opinion, coins and colored Pokemon should be earned with hard work, so I tied them up with training.

NPC Training: Unlocked at Trainer Level 1000
Everyday, you will receive a requests from 3 NPCs to train their Pokemon. They must be done in order. When each job is completed, the NPCs will pay you in coins. (The amount of EXP needed to complete a job will be determined by the level of your highest level Pokemon in your team.)
Bug Catcher EXP Job Formula: (Level^3/100)/[1+(Level*2/50000)]
Bird Keeper EXP Job Formula: 2(Level^3/100)/[1+(Level*2/50000)]
Dragon Tamer EXP Job Formula: 3(Level^3/100)/[1+(Level*2/50000)]
(I'm aware that the formula makes it extremely easy for high TL players to complete jobs, this is just an example formula.)

EXP Examples:
Level 1000: 9,615,384 - 19,230,768 - 28,846,152
Level 5000: 1,041,666,666 - 2,083,333,332 - 3,124,999,998
Level 10000: 7,142,857,142 - 14,285,714,284 - 21,428,571,426
Level 20000: 44,444,444,444 - 88,888,888,888 - 133,333,333,332
Level 100000: 200,000,000,000 - 400,000,000,000 - 600,000,000,000

Bug Catcher Coin Output: 2(square root of EXP)/(Level/10)
Bird Keeper Coin Output: 3.5(square root of EXP)/(Level/10)
Dragon Tamer Coin Output: 5.5(square root of EXP)/(Level/10)

Coin Examples:
Level 1000: 62 - 153 - 295
Level 5000: 129 - 320 - 615
Level 10000: 169 - 418 - 805
Level 20000: 211 - 522 - 1004
Level 100000: 89 - 221 - 491 (Shouldn't be as high as it should be because the EXP Formula doesn't work.)

There is a 1/50 chance to meet the Mysterious Trainer instead of the Dragon Tamer. A Mew will be loaned to you, and the reward will be one of three Pokemon only available by completing a Mysterious Trainer job.
Here's 3 random colored Pokemon ideas I came up with.
LuminousKyogre
RainbowDeino
GoldenGolett

Each completed job earns you one Job Point. You can exchange job points for useful items or Colored Pokemon that can only be obtained with Job Points.
Example:
Lucky Egg: 10 Points
EXP. Share: 50 Points
RainbowMeowth: 75 Points
CursedEntei: 1000 Points

Additional Rules:
You must leave one slot on your party empty, to make room for the rental Pokemon. It will be assigned to Slot 6.
Only EXP gained from NPC Battles will count towards the Job EXP. (Prevents low levels from completing a job instantly by battling Epul.)
Your Pokemon Roster cannot be changed once the job is taken. (Prevents people from getting a high level from their box after accepting the job.)
You can quit the job if you made a mistake in your team, or don't want to do it anymore. You will not gain any rewards for quitting the job early, and you can redo the it.

Pokemon Selection: Unlocked at Trainer Level 1000
Every two weeks, for the first week, Pokemon Selection will be open. Each iteration of Pokemon Selection will have a Pokemon-typed theme. There will be three colored Pokemon to pick from; and when picked, you must train a Pokemon with the same type. The amount of EXP you need to train will be determined by your highest level Pokemon.

For Example:
Week 1: Grass Type
Pick from these three Grass Type Pokemon
RainbowBulbasaur
ShadowTropius
CursedSewaddle

EXP: 7(Level^3/100)/[1+(Level*2/50000)]
EXP Examples:
Level 1000: 67,307,688
Level 5000: 7,291,666,662
Level 10000: 49,999,999,994
Level 20000: 311,111,111,108
Level 100000: 1,400,000,000,000 (Really small again, because the EXP Formula doesn't work for higher levels. Just a placeholder.)

Additional Rules:
Only EXP gained from NPC Battles will count towards the Job EXP. (Prevents low levels from completing a job instantly by battling Epul.)
Your Pokemon Roster cannot be changed once the job is taken. (Prevents people from getting a high level from their box after accepting the job.)
You can quit the job if you made a mistake in your team, or don't want to do it anymore. You will not gain any rewards for quitting the job early, and you can redo it.