Modifying symbols without reverting to objects

Being able to modify more than just the size and rotation of a symbol would be a great addition. Changing outline, fill, effects, perhaps font...

Like having a more robust "Clone" functionality, and with permanency - that is, a library with objects, from which clones can be generated (like with symbols), but where the "clones" can be changed in many attributes without losing their link, and that at any point can be reverted to the master, if needed.