While B neatly solves 2 problems (there being no way to sell unwanted cards and the Wizard Tower being a but worthless) it does have the problem that there's only ever a need for one Wizard Tower. Ideally I think the Wizard Tower needs a buff so it actually performs its intended purpose. If the cards offered genuine buffs you couldn't just research in the same way the Academy does that would be ideal. Of course it opens a can of worms but cards that offered improved versions of the existing upgrades, temporary luck bonuses, generic buffs to the dragon, faster spawning and a "2 places at once" card that let you deploy the dragon twice could make the Wizards tower genuinely appealing.
It's a balance can of worms of course so I'm not sure such changes could actually be made.
