Hyphenation Markup

[Richard Wordingham via Unicode]

In Latin text, one can indicate permissible line break opportunities
between grapheme clusters by inserting U+00AD SOFT HYPHEN.  What
low-end schemes, if any, exist for such mark-up within grapheme
clusters?

The visual effect I wish to enable can be presented simply as:

 <character-2> line-break <character-1>

Character-1 is a base character, character-2 is a spacing combining
mark.  Without a line break, one would simply see

 <character-2> <character-1>

Alternatively, how might I give general permission for such a break?

Richard.