Thought you should know we added a flyer for Virginia:http://fairdui.org/states/t-w/virginia-dui/
The statute does not require a signature. It requires a written promise. Our VA flyer includes that written promise on it so the officer can see it and even take a picture of it if he wants to.
Your advice to orally invoke the 5th is problematic because the officer can say your speech was slurred. We advise remaining completely silent.
Your point about ordering people out of the car "for officer safety" is not limited to VA. That's from SCOTUS - Pennsylvania v. Mimms. But it was in a traffic stop (i.e. reasonable suspicion), not a suspicionless checkpoint where police are more limited and required to follow narrowly tailored written guidelines.
Even in a traffic stop, an officer's assertion of "officer safety" as a reason for ordering the driver out of the car is subject to cross-examination.
"What did the driver do that made you feel unsafe?"
If the officer's reason is that the driver asserted his constitutional rights, a lot of judges will reject that.
Mimms is a bad case for defendants, but that doesn't mean we shouldn't challenge police on it.