I wonder if there would be some value in creating a variable, perhaps 
ALLDISTFILES that would contain all of the possible distfiles for a 
package.  The case I'm thinking of is where the correct distfile is 
platform dependent.  For example the acroread packages.  By listing them 
all in one spot it seems like you could

a) make it easier to regenerate the 'distinfo' file

b) make it easier to mirror all the distfiles.

Alternatively maybe there should be some variable (MAINTAINER_MODE?) 
that would be used in the package makefiles like:

.if defined(MAINTAINER_MODE)
DISTFILES=      foo_x86_linux.tar.gz
DISTFILES+=     foo_sparc_solaris.tar.gz
DISTFILES+=     foo_mips_irix.tar.gz
.else

# normal logic to find the correct distfile based on ${MACHINE_ARCH}
.endif

Comments?

-Dan