So...while I was an avid (and poor) MTG player, Vanguard was released. As I was too poor to purchase any of these fun cards, I created Deckguard (local play style). Throughout this I will reference MTG terms as they are the most universal.
As HEX is digital, this is something easy to implement into programming. Its the modess description that would be a beast. But thats why someone somewhere gets paid the big bucks to do.

Deckguard concept: Random card from your deck gets drastically pumped up pending what Type of card it is.
I will use the following format to layout the actual uses for play (yes it can get crazy, and there are TONS of options...but was fun to play in any style Emperor, 2HG, cube..best ever was a 19player game with no radius limits for spells/attacks).

Type of Card: Given Ability based on card type
-Choose only one of the following listed abilities to give your card (choices based on type of card)
-Once chosen, this ability remains until the player is removed from the game

Given Ability for all Deckguards: This is a constant regardless of type
- All Deckguards can be destroyed, but not removed from game. If a deckguard leaves play it returns to play/hand (depends on card type) at the end of turn. Yes this means you could sacrifice it every turn, use it for cannon fodder, block big mobs, cast it, retarget it, etc. Enchantments on a Deckguard do not return if the deckguard is destroyed/removed from play.
- If the deckgaurd is "removed from game" then it does not regenerate till the end of YOUR turn.
- Deckguards must remain revealed and visible to all players, regardless of type and/or location (play, graveyard, removed from game, etc)
- For abilities that activate or happen when something comes into play, they occur every time the deckguard returns to play from the graveyard

Lands/resources: Start in play and available for use. Does not count against the "played" resource limit. If destroyed returns to play at the end of turn, available for use.
- Produces one of any color resource.
- Produces two of its color resource.
- Counts as a 1/1 artifact creature, a permanent of its original color, and still produces 1 of its original color resource.

Spells (Instant, Sorcery, all non-enchantment spells): Starts in hand. Does not count against max hand size. Once cast returns from graveyard to your hand at the end of turn. If forced to discard, return to players hand at end of turn.
- Reduce Casting cost by 1 Color (Red, Green, white, blue, black, colorless). This could reduce the cost to ZERO casting cost. This spell can still only be cast once per turn.
- Cast spell twice per turn at normal casting cost.
- Cast spell three times per turn at the cost of one additional colorless per cast (first cast= normal cost plus 1 Colorless, second cast = Normal cost plus 2 colorless).
- Turn spell into an instant (spell is still only able to be cast once per turn)
- This spell now counts as an artifact creature with power and toughness equal to its total converted casting cost. If this option is chosen the creature starts in play. The spell can still be used but is now an activation ability that requires tapping.

Enchantments (World/Personal) and Artifacts (not equipment): Starts in play and available for use. If destroyed returns to play at end of turn.
- Reduce Casting cost by 1 (red, green, white, blue, black, colorless). This could reduce the cost to ZERO Casting cost.
- Reduce activation cost of card by 1 (red, green, white, blue, black, colorless). If this reduces Activation cost to ZERO, the ability can only be used twice per turn.
- Pay casting cost to change the target of the enchantment.
- Enchantment now counts as an artifact creature with Power and Toughness equal to is total converted casting cost. If this option is chosen the creature starts in play. The Enchantment still remains active as if in play.

Creature Enchantments and Equipment: Starts in hand. Does not count against max hand size. If destroyed from play, return to players hand at end of turn. If forced to discard, return to players hand at end of turn.
- Reduce Casting cost by 1 (red, green, white, blue, black, colorless). This could reduce the cost to ZERO Casting cost.
- Reduce activation cost of card by 1 (red, green, white, blue, black, colorless). If this reduces Activation cost to ZERO, the ability can only be used twice per turn.
- Pay casting cost to change to another target creature.
- This spell now counts as an artifact creature with power and toughness equal to its total converted casting cost. If this option is chosen the creature starts in play. The spell can still be used but is now an activation ability that requires tapping. (Think back to the "licid's" abilities, they went from creature to creature enchantment back to creature).
- If destroyed you may choose to have the card return to play or your hand at the end of turn. If you choose to have the card return to play, then it targets a creature of your choice (yours or opponents). If you choose to have the card return to your hand, then you must pay the casting cost to put it back in play.

Creatures: Starts in play, Suffers from summoning sickness. If destroyed returns to play at the end of the turn.
- Creature receives a permanent +1/+1
- Creature receives one basic creature ability: Haste, Double-strike, first strike, trample, fly, hex proof, shroud, Shadow, Lure, Venom, Poison, ETC. (they may be a few I have forgotten about).
- Creature receives ability to block any number of creatures.
- Creature receives one land walk ability: Mountain, Forest, Plain, Island, or Swamp.
- Reduce activation cost of card by 1 (red, green, white, blue, black, colorless). If this reduces Activation cost to ZERO, the ability can only be used twice per turn.
- Creature receives protection from one color: Red, green, white, blue, black, or artifact.
- Creatures power and toughness are now equal to its total converted mana cost. The creature still counts as a permanent of its original color(s), but looses all other abilities.

WOW...That was a lot longer than I thought it would be.
And yes, I have continued to play this mode to current release of MTG. Its still just as fun and challenging.