A quick thought...

B) Preserving capture results from all repetitions

My favorite trick for this is:

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my @captures =
   grep defined,
   ':aa2bb4cc6dd8' =~ m{ \G (?<! \A) (\w\w) (\d) | \A (:) }xmsg;
 dd \@captures;
"
[":", "aa", 2, "bb", 4, "cc", 6, "dd", 8]
[download]

which even works with Perl version 5.8 and without scary  (?{ code }) blocks. Of course, output array organization is not the same as any of those shown in your examples, but this surely falls within the realm of "implementation detail"!