Why don't add another version of upgrades?
So if you upgrade a card in normal way you can't upgrade it this way too, you have the choice.
Normal upgrade(in most case): cheaper card/effect.
The new upgrade could be a bit more expensive but more effective (or not more effective, only had another way of his skill) too. For example: Otyugh: it has 3 hp either but get 2/2 from devour. Or has 5 hp and get 2/2 but it's cost is 2 quanta.
Another example: Pest is 0/4+burrow for 2 quanta, with the new upgrade you get a monster who has 0/2 for 3 quanta, but he absorb 2 quanta (and you have 1 quanta for it, not two).
Any opinion?

Edit: Ohh sorry, i won't look it's a very old topic...