Knightfall event crate, choose character option

How hard would it be to change the crate for these events to allow the user to select which character shards they want?  Or simply check for if a toon is already 7 star and not drop shards for them?

I'm asking because I paid to get shards for appo to move up to tier 3. However, since doing so, we've had two events and both times I was rewarded more appo shards. Sure, I can convert these to some blue currency but I value the shards far more than those.  There is a 25% chance that appo was randomly selected once but it has happened 4 times. I could use shards for any other clone.