Could the plan have worked without Sal's involement?
I think so.
shareThey needed somebody to distract the security when Linus enters the vault elevator.
shareIt seemed like a lot to go through the whole 'Lyman Velga' persona just for a momentary distraction.
shareThere was no way they could have distracted the security guards without saul. If you read the original draft you could see the plot being slightly different, I'm pretty sure those scenes were cut because they needed to shorten the runtime.
http://www.dailyscript.com/scripts/oceans_11.pdf