Have the excess coins become a general "Mercenary Coins" currency. This currency can then be used to buy exclusively Mercenary packs. 

A major issue right now is that all newly released Mercenaries go into the same old pool of Mercs as far as packs are concerned. I feel like I need to sit on packs until the next wave of new heroes is released to make sure I can get them all and to feel like the packs are being wasted by using them on only coins. This 'excess coin' proposal slightly alleviates the issue by creating an additional source of packs.

There would of course need to be a terrible exchange rate. 10:1 would feel terrible, but 5:1 might work okay.

Something will need to be nerfed here. Lady Prestor will often give multiple Kazakusan. Allowing you to chain this effect multiple times until you win the game.

Just load up Lady Prestor, cheap minions, removal, and draw. Maybe even Lorekeeper Polkelt for consistency.

All cards listed are neutral, and so can be done in any class, with the best being Druid and Warlock for the draw potential.

This deck would rely on getting to Lady Prestor as fast as possible

• Druid has access to Capture Coldtooth Mine, and (if Kazakusan isn't in deck), can guarantee Prestor is drawn.
• Warlock has large draws in Dreadlich Tamsin and Backfire.
• Demon Hunter had a whole expansion based on drawing cards.
• Priest has always had massive amounts of removal. Slower, but could still work.

If there's ever a decent Fel spell printed, this has a chance of seeing play. Not this expansion though.

Now, with Felosophy, you can copy the card that copies a card!

This card provides a lot of value in reality though, but no card worth copying at the moment.

Warlock version of Garrote. This doesn't do anything the turn its played, but gives quite a lot for only 2 mana and I think this will see play.

Good in Zoolock. Being able to turn that 1/1 Imp into a 4/4, for 3 turns, will be really powerful.

Really strong! With 2 casts, it's Reno the Relicologist, without the deckbuilding restrictions. Also a Fel spell so has synergy with other card effects as well.

I like this. Needing the armor stops this from being played too early, and later on its just a better Flamestrike.

This will end up being broken. Shenanigans with Faceless Manipulator, Mr. Smite, or something will happen because of this.

Great for Control Warrior to stall against Aggro decks while they build up whatever they are trying to do.

Really good with Blacksmithing Hammer, being able to grow it and tutor it out quickly.

Forces removal from your opponent. Unfortunately that's not a tall order with only 3 Health.

Basically Spare Parts. This only sees play in the new Inner Fire Priest deck.

3 cost 3/4 that heals 5? Amazing!

Also some niche uses in classes like Warrior that had a couple Frost spells and can make use of the armor in other ways.

This can actually be decent in something like Token Druid that can buff low cost cards. Functions similarly to Crossroads Watch Post, but summon another minion instead of buffing what you already have.

Sounds great until you realize you'll never get an Honorable Kill with this thing.

That's a big Beast! Basically a weaker Ragnaros the Firelord, that only has one shot. Trash.

Comparable to Voodoo Hexxer, and I think this only sees play in the same class as that card.

Way too slow for Handbuffs, and not to mention much too weak. +2/+2 to your hand for 6 mana, locked behind actually dying, is awful.

Arena card. Personal Opinion, but not a big fan of Honorable Kill effects that can only trigger once. It's almost as if this was made to rush into two things, in which case it probably doesn't live. At 5 mana, that makes it a worse Restless Mummy, and that card was power crept this expansion.