I understand your reservations.
If a exfansion happens I imagine it as community submitted themes and mechanic concepts and not as a chance to offer finished card designs. Therefore the opportunity to design a specific card with your image on it still remains as a very unique opportunity. Having a card with a player's image as the art is also a perfect opportunity to use photographs artfully altered using photoshop. I propose that a group of individuals deemed capable by the community head up Theme Development, Art Direction, Mechanic Design, and Development (Playtesting). We could have a mishmash of desperate designs and themes or a coordinated, cohesive balanced effort with the proper organization.
Initially I'm not a fan. Mostly because of the logistics.
1. If there is a fan expansion... People are already designing their own cards.
2. If we want people's face on the card, that'll involve commissioning new art. Which who is paying for that?
3. If people are making their own cards why wait to win a tournament?
4. Who is acting as the developer that your supposed to work with?
Honestly this comes down to not only a question of how many player designed cards but if we can even do them at all.