You got a point there.
1)&2) Multiple Players:
-why not create a wizard for each player that represents him - with the model's current life being your life count.
-> So each wizard is clearly seperatable (and by choosing the hero from a tavern at the beginning of the game you could determine which deck a player plays).
Also makes damage spells easy to use as you choose the target (caster) and you're happy
3)When a player has an ability in his spellbook that allows him to draw cards, you could check what slots in an array (the 'deck') are still free and pick a random one that will add that spell to the currently available ones.
4) Attack system: Units are paused until a player declares an attack and blocks are done. Now, those units are removed from player control, get via trigger a 'attack unit once' order and are unpaused; moving to the targets they shall deal damage, then moving back to their position if still alive.
Or, when a wizard (player) is attacked, that wizard gets a casting animation so that it looks as if the unit is teleported back to another part of the map (I'd suggest a scenic battlefield for this rather than a true differentiation into different zones.. is not 100% accurate, but will give a much better feeling, seperating it from just being copy/paste mtg card game into a limited version with some graphics). For dead units, there could be a targetable dummy be created - when a player plays 'zombify' on that pillar, he gains that unit again or something like that.. Could be more interesting than just putting units from 1 area to another - oh, and while at it: tapped units could simply be set to sleep =)