if ya don't want to implement all 3 attributes, maybe... 1) finding at same speed as jolly (2x), 2) always finding double-sized deposits, and 3) chance of faster deposits (50%?). I'd agree that just larger deposits adds very little new/special.
Otherwise, (we) always could use a geo that did something special for all those new deposits we need, like granite, titanium and saltpetre.