What?
A direct extension of the Brand and Image idea, this would let the alliance an airline is a member of have an impact on the image of the airline and - consequently - vice versa. As such, alliances would not only have to take great care to harmonise their product (see shared fare rules or shared service profiles) but to also make sure that any new members adhere and stick to a general “image profile” that fits that of all other members. Otherwise, this “image dissonance” might cause negative or “muddling” effects on the image of the others.
Why?
As this feature would have rather soft and long-term consequences (as in: mistakes are hard to reverse in the short-term), this would give a lot more purpose to alliances and make alliance membership something to seriously plan and consider…on both sides of the table.
When?
TBD, depends on the (at this point) highly speculative Brand and Image idea.