Is it possible to crystallize a solid ingot of metal from an (acidic) aquaous solution?
I think you've just described the general concept of Electrowinning?

There are a large number of ways to recover metals from solutions or molten salts.

Producing monocrystalline metals is a different matter - crystal grains in metals tend to be microscopic, but there are techniques that permit growing large crystals of metals such as the Czochralski process or zone melting. Monocrystalline metals sometimes have attractive mechanical properties not achievable in polycrystalline metals - for example, Callister Materials Science and Engineering 6e p. 225 has a nice photo of a single-crystal jet turbine blade that is highly resistant to creep failure with respect to conventional blades.