Orders shipping merge

Hi
It happens that regular customer wants several orders to be shipped in one package and thus save on shipping. So I think it would be a good idea to let customer choose an existing (not shipped yet) order where new one can be assigned.
I haven't found anything like that and I guess it's quite complicated matter to be implemented as a plugin.
Do you think it makes sense to have this in core functionality?

(I can't speak to "...have this in core functionality", but...)

Shipping Director should be able to do this (see this example blog).