It would probably be better if they bootstrapped by building a two stage unit, first.
Isn't the whole point of the Skylon to build the first hybrid engine that breathes air in the atmosphere and uses its own oxygen once outside it? A two-stage unit would just be building the easy parts while avoiding the hard parts.
I actually think they're doing the right thing here. Solve the hard problems first. Build this new engine, and then worry about building a ship to put it in.
To build a flyback first stage would avoid making any hard part. The problem is that it would increase operations costs.
Check the expected costs. It is hard to get mega-projects like that working. The traditional solution is to build a little, test it -- and then build more.
Compare the cost for the whole project with the cost for SpaceX. Or one of the classics -- an air tanked system with a few jet engines.
Point is, you can get lower launch costs -- and with less development danger.
Isn't the whole point of the Skylon to build the first hybrid engine that breathes air in the atmosphere and uses its own oxygen once outside it? A two-stage unit would just be building the easy parts while avoiding the hard parts.
I actually think they're doing the right thing here. Solve the hard problems first. Build this new engine, and then worry about building a ship to put it in.