Remember how great the map system worked with the original Tribes? Unless the mapper edited the terrain (he could add all the buildings/weapons/etc he wanted), the user didn't have to download a thing. It made playing custom maps great, and I wish more games would have taken advantage of it...
That was also Tribes biggest disadvantage as far as custom maps went. Sure you could reuse the same bases and terrain to make hundreds of different maps, but that ensuured that nearly NO ONE played the TRULY CUSTOM maps, with custom bases, terrain, and models. Why download new maps externaly when you can autodownload server side maps that are under 100kb? It made for lots of variety, but very little truly creative NEW maps. Aside from a few exceptions, that was the case in both Tribes 1 and Tribes 2.
This will not be the case in T:V, and I for one am very happy about that. I was fortunate enough to be one of the very few people who had custom client-side maps in regular server rotation in T2, but there were TONS of truly awesome client side maps that never saw any play time, because of the server/client side distinction.
I predict many exciting fully custom maps within a few months of T:V's release. (hopefully I can manage to finish a few of my own by then)