Terraforming with the pick and rake and bare hands becomes a problem of trying to get smooth results rather than pock marked over and under.
The shovel LMB would get the same amount as the pick but from a wider shallower area for a smoother result. RMB attack would be used to drop whatever material you have put into your ammo slot but again in a wider area pile than your bare hands dropping the material would be.
This leaves the shovel to be the tool for a much smoother surface that becomes more suitable for raking perfectly smooth , or is good enough for cave walls. This is similar uses that the shovel had in Planet Explorers and Wurm Online.
You could also add a spade counterpart to the shovel that cuts out blocks and replaces them - using the ammo slot as the field proxy for not having the block workbench, with the limitation that you can only get the natural textures of what you are digging. This would be used instead of the shovel where you want to cut and place smooth squares. Removal works like the sledgehammer but on natural landscapes not block constructions.
While I think it is unrealistic for a shovel and spade to be used to shape and dig stone - we can already shape stone with our bare hands so I would not restrict the material list - save that for realism mods.
Like existing tools make tech tier versions available as we get better ores.