To the extent allowed the Balts and Ukrainians did help the Nazis, especially when it came to implementing the Final Solution. If the Nazis are nice to these folks policy wise until the Soviets are defeated, which is possible, they can string them along for a while and then throw them under the bus. Of course this sort of thinking, basically "do whatever it takes to win the war and THEN trash the Untermenschen" was foreign to Nazi thinking. The effort put in to finding, transporting, and killing 6 million Jews (to say nothing of Roma & Slavs sent to camps) detracted severely from the war effort, and using them as forced labor in a more rational way would have been helpful. The "War Against the Jews" (title of a book by Davidowich), and by extension against other subhumans, was seen by the leaders as every bit as important and URGENT as defeating the Red Army. In spite of that you did have things like Vlasov, but Nazi policy never really rationally examined how best to win the war first. Once the Soviets are behind the A-A line and the west stalemated, then you can doublecross your former helpers.