Interupter lever can pe used on their own. The cable end rests at the brake lever body
yes but the soldered end to fit the ball on the end of the cable is stiff.
and every time there is any bending there, it is closer to breaking. failure .
that is why brake levers made to be on the end of the cable keep the end straight,
and flex in some other way. .. a pivot , or let the barrel end float in rotation..
drum brake front hub? proper brake lever..