I like the costume idea. It works well at Disney, so why not at Alton?
Because it would be too difficult to manage.
What happens if one team member, on Oblivion, needs to work on another ride like Heave-Ho? He wouldn't have the right "costume" and it's just not practical to give everyone each of the costumes (thinking cost here).
The other reason it works well at Disney is because of underground tunnels. This means you don't see a cowboy walking through a space zone to get to a green room or something. Alton doesn't have underground tunnels, so having some high-tech industrial type people walking through the farm yard just won't be good enough.
The last thing to consider is that I should think Alton want to be a united front. Red is the most obvious (as in, it sticks out a lot in a crowd) colour (ask people who work in theatre and why do you think Billy Butlin chose RED?), so the staff are easily recognisable and it's highly simple to see, they are either staff or not.
That said, it would be good if they could impliment it, make it more or a different world.
Just some thoughts.