There's no reason you cant have cat people, beastlords, and berskers in Classic even 1-50 classic. Start em in Kerra Ridge, or their home towns, and its totally do-able. Just got to move a few trainers around and disable some skills/tomes to higher levels.
Give zerkers basic axes and head crush and disiplence at 50-60
Give BLs a slight hybrid nerf.
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Also add warrens.