The X-ray (and other scanning) units are already at some crossings. Seen them, I was impressed. And it's not only x-rays; they can scan for anything, even biologicals.
Flack... Gee, what happens if you get caught? For starters, you get to see them take your vehicle apart. And I mean APART. They dont have to put it back together.
Then you get to have a VERY LONG CHAT with someone in uniform who has no sense of humor. Whatever schedule you were on just went byebye.
What happens after that? Depends on how they feel that day and what else has happened elsewhere in the world to change the current alert status. Let's say you wont enjoy it.
Oh, good luck getting a decent job in the future. Your name gets flagged with at least a record of some sort, and it will show up to haunt you. Or you could wind up someplace where that wont matter for a few years.
The only difference between the US and the Canadian side (when they catch you) is how politely they will tell you how fucked you are.
Sounds scary and overdone? Maybe.
Does it happen? Yep.
Is it witnessed often? Nope, they at least try to be discrete and destroy your car in an enclosed area. It's the only nice thing they do.
So let's do the math; about $1000 of airsoft gun and stuff. Add $20,000 for the car. Add whatever fines they toss at you. Add the loss of income while you sit in a locked room. Add the extra loss of income from the jobs you'll never get. Do the math and decide if it's worth it.
Guess what? This shit can happen, and all they have to do is feel like tossing the book at you.
(Got to love working for the Government, you get to see documentation that's fascinating).