What is the reason for the following restriction:
"EXPORT_FUNCTIONS must be used at most once per eclass."

Eclasses could be cleaner if the following was allowed:
   EXPORT_FUNCTIONS src_unpack src_compile
   if <some EAPI condition>; then
       EXPORT_FUNCTIONS src_prepare src_configure
   fi

Looks like none of the three package managers would have any trouble
with it. (And it's used in the tree already.)

Ulrich