[fburnaby]

I have to disagree with other responses. I think you could make a career of this for the same reason management consultants can.

You could swoop in and "fix" some stuff and then leave the in-house team not understanding what you've done. That sounds profitable. You might even get called back to fix things a second time.

As with management consulting, I think it would at the system level tend to do more harm than good, even if you do good work and get paid well for it. I agree strongly with feoren that the code needs to reflect the in-house developers' mental models of the domain or everything will fall apart. If you fix things and then give them a bunch of processes and coding standards to follow, they will not do well and you will be thought of as some clueless architecture astronaut by them. But profitably.