Personally, I think field targeting would be a nice mechanic to add. As others mention, the main trouble is the automatic positioning system. Adding in cards and / or abilities that allow players to move / shift creatures around the field would be an easy fix.
For example:
Wormhole ability:
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shift target creature to a random location on the field, usable multiple times in a round.
Astral Shift:
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this creature switchs positions on the field with target creature you control
Shadow step:
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move this creature to target slot on the field.
etc.
Such abilities or spells would allow players to make full use of field mechanics which I think it would add a nice layer to the game.
On another note,
Moomoose had a nifty idea for a series of field targeting cards:
See thread in: Card Ideas and Art ยป Stone Totem | Earth Totem
He's proposed one for each element. They add a small buff to adjacent creatures.