I don’t think I’ve come across any examples where the Western Allies created any sort of “German” unit. Yes, there are the significant numbers of German refugees who wind up supporting the Allied cause. But they’re, if initially only eventually, sort of wrapped up into everybody else. They certainly ultimately become regarded as English-speaking anti-Nazis, to become incorporated amongst all the others. Yes, the fact that they could speak German and were often otherwise specialists did tend to skew what they were assigned to.
But the average captured German soldier? Yes, the lower ranks could usefully be assigned as POW labourers. But as combat troops? It’s probably significant that it’s surely rather late in the war - the last year in practice - that the Western Allies could start to capture Germans in large numbers. By that stage, was it worth trying to turn them?
The situation on the Eastern Front may be another matter.