Ld cards are very different. You can't buy them in packs, you can't sell them, you can only have one of them. They have no impact on the market and they have no impact on the packs.
But other cards do have an impact on the market and the packs. Upgraded cards would occupy the space in the New blood pack and decrease its value and sales. Why would people buy new blood packs containing the same cards they already had?
Changing clans creates a lot of confusion. Cards are created for specific clans only. So cards changing clans might be good for the story but bad for the game. e.g Saki changing clans would be disastrous.
Cards like Kiki Cr and Kiki already create a lot of problems: http://www.urban-rivals.com/en/community/forum/?mode=viewsubject&forum_page=0&id_subject=1586594&subject_page=0#answers
Even Slightly changing a card requires a good amount of effort so i don't think changing about 100 cards stats would be an easy walk in the park.
It's like you didn't even read what I said in my initial post.
My suggestion was that the Upgraded cards would be introduced like the Lds were. They wouldn't be in packs, you'd complete missions to earn them.
And it wouldn't be EVERY old card that would be upgraded. It would be one per clan, voted on by UR players.
UR staff have done this before with Ld cards and it worked out well for everyone. My suggestion was to try something new now that the Lds are all released.
Just to clarify, so anyone who comments in the future know exactly what I'm suggesting:
1) UR staff picks ~5 outdated characters from a single clan, and player vote to decide which of those characters receives an upgrade.
2) UR staff creates a newer version of the old character, and makes it available to players who complete certain missions or achieve certain goals. Same rules as Ld characters apply.
3) Repeat for each clan, once a month or so, until every clan has an upgraded character.
4) Newer clans like Frozn or Berserk, or any new release clans after the start of Upgraded characters, will be chosen by UR staff without players voting.
In the end, 22 new characters that replace old, unusable characters.