I dont know, most of the custom maps are not designed for line battles. That is, actual line battles, if you mean by line battles "organized battles", then sure. My vote goes to Conquest, not sure how many maps support it though, I know mine should.
Indeed, some more maps may need to be made. I really wish Russia 3 maps would port in properly..I have a ton of really awesome old ones that were made for that mod =[