Yeeeah, you know how a dispenser with TNT and an iron ingot spits out a TNT block?
we should have something similar for minecarts. when you put a minecart and something else (a diamond?) in a dispenser, it dispenses minecarts.
however, these minecarts are special.
when you break them, they don't drop a minecart item, and you can't have more than three minecarts from that dispenser at the same time (to make sure nobody can crash the server with excessive numbers of minecarts). this would make for good rollercoasters, highways, etc, and would rid users of having to bring a minecart with them 24/7.