Worse still, it wouldn't be just that one module. What would happen is that, due to the excess load on the 5V line in that ribbon, it could overheat and catch the ribbon itself on fire. This would then lead to a bunch of cross connections and shorts, leading to circuit damage and more fire. This would, due to the tight quarters inside the cab, catch even MORE things on fire inside of it...module boards, components, ribbon cables, etc. About this point, the amount of smoke coming from any opening would be apparent...but then, given that we're talking about a sequence of events that might take about 15-30 seconds, by the time that smoke's streaming out of the case, everything inside would be pretty royally boned. Plus, if you have no open panel spaces, putting this flaming monstrosity out would be difficult; yanking the power would stop the electrical aspect, but by that point the materials themselves would be on fire.
Some power supplies and/or modules actually do have overamperage cutouts...but not many that I can think of offhand. So, the hard and fast rule is that you have to know your wire gauges inside the ribbons, know your current draws per module, and never exceed the wire's current handling capacity. Doing so gets expensive.