I like the Do Win concept, but Don't Lose is pretty archetypical of card games (excluding standard 52-count decks). Could be a combo thing, though, like, multiple ways to win. MTG has their black poison counters and there were other Tap/Spend-to-win effects and stuff, so something like that could be fun.
I still have trouble imagining the gameplay without agreed upon cards, as part of what makes cardgames the way they are is you have to build a deck based on what the manufacturers have made, and it would be super easy for someone to be like "Now I pull out Penultimate, Epic, Something-or-Other the Unbeatable! who has the ability to void all other effects on the field - monster, magic, or otherwise - and takes it's total attack from the number of cards in all decks combined ever with equal defense and quadruple the health (oh, and not to mention, he's so big he has his own force of gravity so you can't hit anything else, not even the player's HP directly, and all the gold and objective materials and stuff fly into his field to be added to his horde)." lol. I think the Win concept and having character's describe their deck in their character sheet will help, and so will some strict guidelines, but that's my concern.