I think a way longer train on a strictly straight track would work in maps that have rails from one end of the map to the other -Its terribly vulnerable to tanks ans such as its so long (Although I think only its front-most cabit should be destructible), with the rear ones being wooden to carry troops (Although, with BF2's penentration, mg bullets and HE should be able to kill those inside)
Needless to say, a strafing run could kill alot of people in the rear cabins
A map like Stalingrad could have one in many map versions for getting the troops from a safe point to the front.
For some maps, the rail could stop at a point, so that it doesn't cross the entire map, but simply moves men from the rear to say a frontline base
A new system to aid this will be stops that are removed across the rail so that with each flag capped, the train can move further down the track
I like the train we have as 'proof of concept' but that's really all it is - With its funny outside-sitters. It might as well have been a tank with more seats, greater speed and flexibility of motion.
I would also like trains to have more smoke - I know the risk, but its one vehicle - And it eint the 1940s without it...