there r two things for that person whom they r going to meet;
1- who could change course of war..
2- he should know everything.
For tobirama I dont thing any of these point valid. not motto of war is changing by him. and nor he know everything. because he cant know about start of clans. he only know start of village. to know start of clans he should be there when ninja clan started or he should have rennigan (so that he could fully read uchiha stone).