So Jasperwillem raised this in a previous thread but it was such a good idea it needs its own thread. Basically, instead of getting forced to have a new locomotive each week could we just have 2 upgrades of our own choice so that we can have more freedom. There are some situations where tunnels, hubs, lines or carriages would be much more useful than an idle locomotive. All credit goes to Jasper for this idea.
Here is the original thread: http://community.dinopoloclub.com/t/train-line-limit/2147/3