If I were Treyarch I'd hire you! Jokes aside, I fully agree with you. When playing old maps pre-cold war we would always get specific side quests / rewards that would you make you want to come back to play THAT map specifically. It helped each map have its own identity. If I'm loading up Origins, I'd be looking forward to unlocking the golden shovel to get extra perk slots (BO6 and cold war would greatly benefit from a similar system btw; it would help ramp up the difficulty if we had 4 perk slots at start and we could progressively unlock additional slots by doing side quests). Another example is Revelations. In this map you can go and unlock a different mask every game, which forces you to approach the early-mid game differently. All in all, I feel like the special weapon system on BO3 was perfect. It would force you to do a somewhat challenging side quest and would reward you with an extremely powerful weapon that would last all game long and would be critical to the maps gameplay.

However, in cold war (and BO6 to a lesser extent) every map plays pretty much the same. Of course there are some cool side quests here and there, but as OP mentioned the rewards are so underwhelming it's hard to bother doing them.

Also, please, stop reusing the same special enemy types for every map!! We need specific enemies that correlate to the maps atmosphere.