Why go to the extra difficulty of setting it up for the tiny minority that would use it? Where is the cut off point? Just go to the games as you would normally and then get a half-season ticket.
It would inevitably involve a change in ticket selling software - maybe more, which isn't likely to be cheap. It's easy to apply common sense to something like this and think it's an obviously good idea that should be easy to implement, without thinking about any of the practicalities of setting it up or whether it would actually be cost-beneficial.