You can do this but there are a few necessities to avoid a "boiled in oil" outcome (think about all the fatty dripping in the standard loaf pan), and so you can get the loaf out when it is done. Just like crock cooker meat loaf.
You put fine racks across the bottom, so the drippings can drain.
You use 90% lean or leaner beef (normal burger is 70) to drastically reduce the amount of drippings.
You use reduced fat ground pork or pork sausage.
You make a firm mixture with the bread and egg, so you can shape the loaf to leave an inch of space from the wall in every direction.
You use a meat thermometer to make SURE the middle of the loaf goes to 180. But then take it out; if you go to 200 you will lose a lot more juices.
Be careful to thoroughly PAM the cookwell with the new high heat grilling spray, but get an unflavored one.
By the way, a 6 quart crock will do a 6-8 pound meatloaf.