Generally speaking there were well recorded cases of Gulag prisoners volunteering for service in penal battalions (read suicide) the worst job in the Red Army, as soon as news of the invasion became public.
1. Quite understandable if you ask me considering life in a Gulag.
2. Being a red army solider during the first months of Operation Barbarossa was generally suicidal (during battle as well in the case of being taken prisoner by the Germans)
3. One has to take into account that the purges had brought a lot of people into the Gulag who were actually not only supportive of the Sovjet Union, but spent their life building that state. Not only would this kind of prisoner still be willing to risk his life for the Sovjet Union, maybe even for Stalin, but would crave at any possibility to redeem himself (because he was only sent to the Gulag due to some sort of tragic misunderstanding, of course).
---
On the general question of "niceness".
1. The degree to which the German planning from the outset intended to break most rules of civilized warfare in Russia would demand a change of a degree which is impossible to combine with NS-leadership.
2. To make use of such a situation, a complete programme of what we call today "nation-building" for diverse ethniticies would be needed, with a fine balance of X's, Y's and Z's independance and Germany's interests. This would fail due to apprehensiveness on the side of people which have only seen the worst side of history for some time, but as well due to incompetence/over-ambitiousness/greed and other miscalculations on the German side.
3. As had been pointed out in other threads: in how far would the German war effort really benefit. A war economy which isn't producing enough output to beat the Sovjet Union in its reduced state of 1942 couldn't have enough material to arm many followers.
Also, one would have to cynically calculate the costs and benefits of niceness as opposed to the costs and benefits of OTL's genocidal occupation.