RBF
Currently cabin crew are trained to handle fires inside the cabin. This training should be expanded to cover checking for airframe and engine fires after a reject or landing with engine problems - along with proactive communication of fire status with the flight crew.
They need to be able to distinguish between tire/wheel/brake fires where three minutes is allowed before ARFF arrives - and uncontrolled fuel fed fires demanding immediate evacuation.
Not sure what sort of aircraft you are working on or thinking of but a couple of points if I may:
1. From inside an airframe such as a 777 there is very restricted external visibilty. There is Zero/nil/nada visibility of the landing gear from within the fuselage - so absolutely no possibility of cabin crew looking at tire/wheel/brakes etc... and as far as engines are concerned it is only possible to see a portion of the front of the engine nacelles, and if you want a cabin crew member to check engines out they might have to leave their seat, which brings me to :.
2. If you are going to start asking CC to carry out an external check through the cabin windows in the event of an RTO they will have to leave their seats, possibly leaving their door unguarded ( it is often minimum crew these days so often just one crewmember at most if not all doors, even on the wide bodies)... if an EVAC is then signalled from the Flight Deck when the Cabin crew are not at their doors you really are in for a world of hurt or much much worse......
Given that interphone calls may not be answered in a high cockpit workload situation, cabin crew need to be able to actuate an "EVACUATE" alarm that would annunciate in the cockpit and display prominently on the EFIS.
You've effectively got that on the 777 already ( and no doubt on other types) ...the EVAC alarm can be triggered in the Cabin and it gets very noisy on the Flight deck and a big red light flashes...and FWIW at some airlines if not all Cabin crew are briefed that in the event of a clearly catastophic situation they can self intiate evacuation...