Vukassovich was (to quote wikipedia) "Among Austrian generals, he demonstrated above-average initiative and skill" which isn't exactly a ringing endorsement.
However, if adding a Austrian leader and swapping an Austrian LN to a GRZ enhances your experience, great.
The other 2 are brigade commanders, who generally aren't represented and had insufficient span of control to lead other units.
As mentioned, this seems a particularly well balanced scenario as is, so I don't see the need to mess with it.
Glory is fleeting, but obscurity is forever.