How about this. the current challenges are very simple and many people find them confusing so here's a proposition
we can have either or both systems.
-Personal challenges:
Everyone get's a random set of challenges like now.
Challenge re-roll possibility.
No challenge with not yet unlocked weapons.
-Community challenges:
The community working together for the progress
Players need to achieve a minimum criteria of participation
Challenges per categories ex.: "Destroy X vehicles as (double points as Engineer)"; "Revive X players"; "Spot X players (double points as Recon)"; "Capture x objectives (double points as Assault)"
Focus on class diversity and role enforcement