The German "army" that fought from the Scheldt to the end would have to stretch credulity simply too much unless it was outright fantasy. Mobile defense? You realise the Germans had literally next to no fuel at their disposal? I mean, where would be the fun in such a faction, hopeless and outmatched in every regard?
There would be, if and only if, it was done right. Volkssturm infantrymen, domestic and foreign SS volunteers/fanatics, and if you were really throwing historical accuracy to the wind, throw in the Werwolf partisans.
Abilities like "Zeal" and "For the Fatherland" can make a return, the faction would also have a very rag-tag look and feel about it.
Armour would be mainly the occasional call-in but the buildable AT options would be extensive and versatile. Traps, mines, defensive structures would also be non-doctrinal and comprehensive.
Commanders could vary from Urban Defense specialists, with vet Sniper call-ins and road blocks, to Conventional Warfare Commander, who would have access to the few regular army infantry left as vet Grenadiers and Panzer IVs/Panthers, to a desperate "Defend the Fatherland" at all costs commander, with call-ins of fanatical SS remnants which would play like KCH squads, more booby traps options and maybe a rare King Tiger/Elefant call-in. It would very much be a "Battle of Berlin" esque faction.