I don’t really like the new crafting system, because it removed the ability to upgrade cards instead of building new ones from scratch. Well in my opinion it would be really good to add back a mechanic like that, with addition to be able to downgrade cards (just because some people like that).
The cards could be upgraded using credits and fragments, the cost would go like this:
- Credit cost would be the difference in costs of current level card and the next level one (and vice versa)
- Fragment cost would be calculated the same way as credit cost (except for downgrading, where you’d get the fragments back)
Characteristics of the newly upgraded card:
- Same loadout card
- Next/prev rarity
I’ll add an example as soon as I’ll be able to edit it in gimp 
(only if there will be enough interest )