I up-voted both Steven's and Kelly's ideas.
We have this exact same problem.... As a horrible workaround, we use the Registration Type widget and our registration types are "I will book via Concur", "I will request a flight", "I will request a train", "I don't need any travel" etc. Based off their answer, they are sent down the appropriate registration path with only that travel information and type.
I say horrible because this means you have a lot of different registration paths to manage.... If we could have the Air Actuals, Air Request widget(s) etc. appear based off the answer to a question, we could manage all of this within 1 Registration Path.
Thankfully the ability to assign Room Types to Reg Type instead a Reg Path cut our paths in half (that's another story).