Imho, the best solution would be to make a short series of single-player missions. These missions can include some sneak-previews of high-level units and comms - for example, the first unit is a chicken-defense where there are neutral, claimable comms hidden in the battlefield. Each mission includes a wiki-page describing the exact loadouts of the comms hidden in the mission.
Do similar things with high-level factories and other unlockables. Make each player's completion of this single-player campaign an always-visible attribute about the player, and allow servers to define what completion of the campaign is required.
Make it short - ~6 missions or so, like 4 hours of gameplay. Basically an extended tutorial.
So servers can say "I want players who've at least completed the introduction", vs. "I want players who've completed the basic campaign".
The big thing, the big failure of the existing Chicken Defense missions: make it tied into the player's unlocks. Make them use
their comm. Give them a full level for each completion.
