Hi,
One can use digital control on regulating the bias current by using parallel current sources.
Basic comparator to compare the input signal, compare with reference and turn on/off the biasing legs.
One can also add/remove the input differential pair, like one does to get rail to rail input range.
However this will add non-linearity into the system, but can be used for IO kind of circuits, where monotonicity is more important than avoiding non-linearity.
Hope this helps.
Supreet