Quick thoughts on some card options.
Card 1
The Gate to Hell option is a really cool idea. Unfortunately with it being Dark or Holy it does not really fit the whole card (unless something else was added)  I enjoy the other 3 options fairly well. Karadox's suggestion of perhaps merging a couple into one might work really well.
Card 2  The 0 damage to keep guarding (#3) really gets the timmy in me, man there can be some epic turns with that one. (#4) Seems like a great build around as well. 

Thanks everyone who have put in the time to playtest and work on all of this! My son and I can't wait.

I would! I do think the schools are deep enough now that we don't NEED new spells. A full Arena expansion like paladin vs siren is a huge amount of work, which is why we might not see a new one again.  But a new mage card can really open up whole new styles of play.

Perhaps they could make Arena packs similar to Academy expansions. For example, the female wizard with perhaps 6-12 (24 to 60ish cards) new spells that tie in to her abilities. There are several promo cards that can be slotted in as well.

Here's my top wish list

Arena Elementalist:  The academy version is awesome, can actually make academy interesting to play. I would love to see a few more frost spells and an arena version.

Alt Wizard:  It would be nice have another option for arcane. I'm sure some are a bit scarred/sick of the wizard.

Alt Druid: Either a port of the academy or a new alt druid.

Alt Forcemaster:  I guess. For those players 

Alt Paladin:  Huh, I didn't even think of this one! Now I'm kinda excited by it, more Valor!

Anyway I think individual small arena packs for each mage might be more realistic.  But if they did put all the mage cards in one last pack I would buy it up in a heartbeat.