Benjamin would be particularly useful in waving up an engine system - it seems to be his speciality to be able to build wave-tech engines with very little quirk. The worst that's been seen so far is a particular desire for an odd fuel, like the Bullet Boy Express getting its best mileage on imported German beer.
Putting Ben and Agatha together on the Mallard will most likely result in having a central boiler plant with steam engines in the wings. I'm thinking of some bastardized twenty-four cylinder version of the Rolls Royce Merlin, built to run on high-pressure steam. Properly waved, it'll be obscenely powerful and insanely efficient. The only drawback is having a boiler plant inside the main fuselage, but I'm certain that with Agatha's help and a healthy dose of Handwavium that can be reduced to a very managable size.
Putting Ben and Agatha together on the Mallard will most likely result in having a central boiler plant with steam engines in the wings. I'm thinking of some bastardized twenty-four cylinder version of the Rolls Royce Merlin, built to run on high-pressure steam. Properly waved, it'll be obscenely powerful and insanely efficient. The only drawback is having a boiler plant inside the main fuselage, but I'm certain that with Agatha's help and a healthy dose of Handwavium that can be reduced to a very managable size.