559 is the 26" back wheel, the front 406 a 20" (typical tadpole trike layout)
Parts list is showing a Cost conscious Spec of trusty Avid BB7 Cable disc brakes..
1 thing you can do is add; Tektro 107A
spring modulators,, 2 for $10.
It's adopting a use of a V brake noodle in the cable run,
that has the housing compressing a spring,
as you pull the cable.. softening the force initially,
applied, when you pull the lever.. *
It's a QBP stocked Item,
if you want your local shop to get them for you, and install them ..
Might need new cables , if they're cut shorter than needed,
or cut the housing to use the same cables.
* I see them on some entry level bikes, included, anticipating needs,
of people who will feel their front V brakes work too aggressively.
....