If by "the input plugin" you mean Dolphin's normal input system (Dolphin doesn't have plugin support), you could use something like this for mapping L-Digital in order to make the input less instantaneous:
smooth(A, 0.05, 0)
Where A is the button you want to use, and 0.05 is the time you want it to take for the input strength to reach 100%. (Perhaps you want a little less than 0.05.)
smooth(A, 0.05, 0)
Where A is the button you want to use, and 0.05 is the time you want it to take for the input strength to reach 100%. (Perhaps you want a little less than 0.05.)