A problem. Rats are going to chew out of that so fast. Unless you cover the entire front with wire mesh on the inside, the rats will chew out and escape in a matter of days.

You can just throw food in there if you want. Bowls won't work as they don't keep their food in it. They will take it out, bury it and end up pooping and urinating on it. All of my mouse enclosures do not use food hoppers. I just put the food right on the bedding and I do notice quite a few blocks in the bedding when I clean, but it is not enough to make me build hoppers for the tubs.