You need to setup two primitive attributes on guides :
-
templatenames
: string array of feather names that you want to interpolate
-
templateweights
: float array of feather weights, it tells the blend amount to take from each feather template

Most of the work would be adjusting weights in
templateweights
attribute. For example, a possible way would be to adjust a weight attribute for each template, then build an array of all these attributes. This opens the possibility of controling weights procedurally with Attribute Adjust Float node or Guide Mask node, and manually painting weights with Attribute Paint node. You could adjust weights on guides directly, or do this on the skin then transfer to guides using Guide Skin Attribute Lookup node.

Attached a hip file with an example using this approach.