I think it will be great if Strava adds Multiplayer Team Challenges. Here is why it's important:
Challenges are currently single-player leaderboards. It is missing multiplayer challenges.
Strava Squads can form with 2 to 4 players to win badges.
Challenges that are multiplayer mode are even more fun and engaging. Teammates must work together in order to be able to cover the distance of the group challenge. For example, group monthly running challenges can be 300km, 600km, etc.
Strava Squads can challenge each other in Versus Mode (Red team vs. Blue team vs. Green team vs. Yellow Team) to see which squad covers the most miles in a month, climbs the highest, or takes the least amount of time to cover a set distance.