What is the balanced ionic redox reaction of nitrite ions with manganate(VII) ions in acidic solution?
Your suggestion is certainly part of the picture, but as is usually the case with nitric acids, a number of side reactions can and often do take place depending on concentration and temperature. In acid solutions, for example, nitrite spontaneously decompose giving nitric oxide together with dinitrogen tetroxide. My feeling is that under optimum conditions your suggested reaction would predominate