The way to make a proper griddled hamburger:
Start with beef that is between 70/30 and 80/20. You need to use a fatty beef because you are going to be doing a few things that will restrict the amount of juice in the burger and the extra fat will mitigate that.
Season your beef and roll into balls less than 1/4 of a pound. Let the size of your patties be determined by the size of your pan, you need them small enough that once you smash you won't be touching the sides of the pan.
You then want to preheat your pan. You want your pan to be as hot as possible. A commercial griddle can range in heat between 375 F and 650 F, so the temp here can vary quite a bit between places, I find hotter aids crust formation and allows the interior stay closer to medium.
Do not use oil. I can't stress that enough. Your beef will put out plenty and oil will fry the burger instead of allowing a seared crust to develop.
Place your balls of meat on the pan and smash them flat with a spatula. You might need a second spatula to remove the patty from the smashing one, as you lack the space space to heat it like you would on a griddle to prevent sticking. Allow it to cook about two to three minutes, then flip and top with cheese, if desired. Two more minutes and remove.
As an added bonus, you can toast/fry some bread in the beef juices to create a patty melt style burger that will be oozing beefy goodness. You can drop the bread in right after the flip and it will be perfect by the time the patty is done.
It strikes me that it would be a bit overpowering, and that even with a binder you would have a hard time keeping it together. Cured ground beef just seems like it would be nasty :-)
I've experimented myself with two 'inclusions' in fresh beef patties. One is bacon (cooked), the other is salami. They are both interesting, and if minced finely and added to the grind they do not interfere with texture but add some excellent flavors and saltiness.
I would imagine pastrami would give you a nice result as an inclusion too. I'd chop it up and mix it in with the cubed up beef before you run it through the grinder.
With burgers really the fresher the better. I grind about 2 hours before grill time, and that is only so I can throw the patties into the freezer. I like them thin and cooked through, so I need to freeze them so they hold their shape better during the first side cooking. If you like your burgers to have some pink you'll probably want to skip the freezer.
Best Answer
Does your burger recipe rely on the center of the burger being medium rare? If so, you may have a problem with the spice ratio because your cooking technique will produce different types of doneness on the grill vs. the griddle.
With the grill you get a higher quantity of crispy burny bits (the Maillard reaction) than you will on a griddle (temperature generally in the high 300s F, as opposed to much higher grill heat). With the grill at home you can go for a rare to medium rare center. with a lunch truck, you had best go for medium well for safety's sake (and possible legalities).
The easiest way to know how your recipe will work under griddle conditions is to test it. Make up your burger, pat it thin and cook it all the way through in a medium heat fry pan (not my favorite way to have a burger, but classic griddle approach). If all is well, you're done. If not, well, you've already perfected it once, you'll need to decide what changes need to be made.
But I'm betting that perfection will carry through to the griddle burger just fine.