Carvan Carts used to be very easy to find in 2238. The Khans used to use these carts to lay traps in 2238. Get 10 guys together, go out in a caravan, get an encounter, and wait for PK's to drop in.
Carvan carts also used to force other players quite successfully.
I suggest the following:
#1 = Carts should disguise/hide the name(s) of players who are in the caravan!
#2 = A series of basic and repeatable quests are available, so long as you OWN your own Caravan Cart. Far Go traders for example will hire you to take "boxes" in your caravan to the Den or wherever, and will give you several days to get there, and there will be large pay outs. (Once per 24 hours up to 100-200k? or maybe staggered amounts depending on your success ratio?)
This gets players in large numbers, moving together on the worldmap, in RT or TB (their preference); and advantage is to the defender. Should raiders "capture" the box, they can sell it for a small fee at the Raider base location. or something like that.
Would make for some epic caravan battles.
You could also restrict the amount of these quests given out, (max 5 at a time), and have a separate counter like TC, indicating that somewhere between HUB/DEN or whatever locations, there is a player caravan on the road.