Add more ways to spend runes

Upstartes

Unless I've missed something, right now the only thing you can do with runes is level Planeswalkers (I think, unless I missed something). So, if you have all your PWs maxed, runes are of no value - except for saving them up to level a PW you buy in the future.

Clearly the purchase structure has been set up such that things are only "purchased" with crystals, and that this is part of the monetizing of the app. I'm ok with this, and I'm not asking that we be able to by cards and PWs with runes. However, it would be nice if there were some other things that you could use them for so that when you win them, you feel kind of pleased instead of the current situation in which I just don't care at all.

Here are a few ideas I have thought of:
* Buy a "mulligan": spend runes at the start of a game to reset your hand and/or the board.
* Select opponent: spend runes before a game to pick which type of PW you want to play against during that game.
* Open an alternate pack of cards: After opening a pack of cards, spend runes to throw away all the cards from that pack and open a new pack. Allow this only once per pack.

I'm sure there are other ideas that would work. I'm less interested in exactly what the runes would be used for as in just having something that makes them feel a little more cool.