Here are my current suggestions for more SRFI 146 procedures:

Constructors: mapping/ordered, mapping-unfold/ordered

These are the same as mapping and mapping-unfold, except that it is an error if the keys are not in order, and they may be more efficient.

Copying and conversion: alist->mapping/ordered, alist->mapping/ordered!

These are the same as alist->mapping and alist->mapping!, except that it is an error if the keys in the alist are not in order, and they may be more efficient.