I fear the answer is going to be: write your own node to do that.

I find I want to achieve a couple things:

• have a standard launch file deployed on all vehicles to bring up vehicle-specific nodes, this being called by the highest launch file
• have a general launch file on the core to bring up everything, including vehicles when they are active

Is any of this achievable? Right now I tried launching a launch file with one of the defined machines offline and the procedure stopped completely.

Ideally

$ roslaunch project.launch
   (search for machines, found 1 through 3)
    |||
    ||\_ machine.launch (on machine 1)
    ||       |||
    ||       ||\_ laser
    ||       |\__ motors/odometry
    ||       \___ amcl
    ||
    |\__ machine.launch (on machine 2)
    |
    \___ machine.launch (on machine 3)