My background is more deep-rooted in handheld games like Final Fantasy Tactics, Pen & Paper RPGs such as D&D, Immersing Video Games such as TES: Morrowind and online games which permit freedom of player choice (Minecraft, Wurm Online, Entropia Universe), dungeon crawlers with RNG elements (Diablo 2, Diablo 3, Darkspore, Torchlight, Path of Exile) as well as TCGs such as Magic: The Gathering. As a designer, these prospects are what mean the most to me.
My current project, Fabricant TCG, is still in it's planning stages.
In the beginning, I start with a single question which will spurn my ideas. What makes these games so enjoyable for me?
The answer would be creativity, something each of these games have in common. The freedom for a player to be creative with their character(s), surroundings and community. There are other qualities, such as surprise, strategy and variety which could add to this, and many of the games I reference embrace this concept.
Final Fantasy Tactics allowed your character to change roles, learn and combine new powers, so much so that the possibilities were nearly endless.
D&D allowed your character to progress and use one's own ingenuity to decide what the best course of action in progression and combat would be.
Morrowind gave you a large set of tools to interact with other characters within the world, and even allowed your character to progress and learn new, often player-created powers.
Minecraft allowed you to use your imagination and creativity to create whatever you could imagine.
Diablo allowed you create and nurture a dungeon delving hero that could quest for randomly generated equipment and explore randomly chosen levels, allowing endless replay value.
Trading Card Games allow one to create their own set of weapons and characters to play with against friends with an innumerable amount of strategy and variety, with a brand new set of rules for every other TCG.
Putting all of this together, what might I come up with for Fabricant TCG?
I would come up with a way for you to create your own Spells, Characters and Weapons with an endless variety of components while allowing a system with complex strategy that could frequently change it's course as the game played out, keeping you engaged with fast-paced bouts of action while being weary of what creation your opponent may unleash next.
Using open-ended creativity, what kind of system would you create?
One of my other projects, 'Souls' is a TCG where you have three blank cards, each of which are designed to be slotted with different cards. Each card has 4 slots, of which you can add in any combination Mastery, Heirloom and Talent mini-cards that determine that card's abilities. A 5th slot is used as an 'Aspect' which determines what Ability Cards your characters can play on their turn. I.E. A Staff Mastery, Spiritualism Talent, Pointed Hat Heirloom and Dragon Bracelet Heirloom Monk Aspect would be able to use Monk ability cards that required 'Staff Mastery' while having bonuses during combat from the Talent and Heirlooms. It would allow a player to customize each character individually while adding further depth with Deck Building.
I did hit some roadblocks, noting that the way the game functions may have to change considerably if you were to add a resource system as well as minion cards. The reason all of the cards aren't custom is mostly to make sure you don't have to design 43-63 cards with up to over 250 pieces in total just to play, and to note that it may be tacky to have a deck of 40-60 cards that each have up to 4 components that you have to slot. Lastly, that would mean all of your cards would require sleeves to hold in component cards, or you would need to come up with another method such as velcro, 'cardboard frames/sockets' or glue, the latter many dislike. Another option is having only some of the cards be available for slotting. Of course, if the game were Online, everything would be far more simple.
A standalone game with guidelines to create your own cards is not all that far-flung of an idea. One could simply state that X type or rarity of card has X points and every stat or ability on a card costs Y of X points. The difficulty would be that it may be difficult to get started (if not online), unless the system used fewer card decks. I could see 20-card games working, but anymore than that it may take one over an hour to create their deck, though this never stopped games such as D&D.
My suggestion would be to add a whole layer of depth, turn it into a pen & paper RPG CCG or some kind of dungeon crawler. Players develop their cards as they play, playing against more powerful individual opponents using their decks. Perhaps combine elements of your Wizardry and CCG project together somehow?