Card leveling ideas

One of the ideas I've been thinking about a lot for Card Creatures is to have a player's cards "level up" when they are used a lot. As an rpg fan this naturally appeals to me (and could be similar to the leveling system in Tetra Master), but I also think it opens up some interesting gameplay possibilities. In particular it could be fun if you got more points for capturing a high level card than a low level one.

We have already discussed the idea of cards being created in basic categories of increasing strength. This would probably mean that a strong card would start out at a higher level than a weak card, though the weak card could be leveled up through use to be more competitive.

The main problem I see with this idea is that the game rules would then need to reflect the higher-numbers-are-better idea, since you may remember this not always being the case in Triple Triad, where you could lose to a couple of well placed weak cards with rules such as Plus or Same-Wall.