I think this is a good concept, but might require a little lower cost for Convalesce. I suggest that you drop it to
for both unupped and upped.
Reasoning: the card is balanced as it is (unupped has 1 attack and 1 drain for 1 cost, balanced, maybe a little "strong", but since it's drain 1 instead of vampire I think it's fine, it doesn't warrant an increase in cost; upped has 4 attack for 4 cost and heals 2, plus its ability is slightly more powerful than unupped. However since it's upped a -1.5 cost reduction is fine). The ability completely changes the card and turns it into another creature. That means that, effectively, the first part must be balanced regardless of the second, maybe accounting for a small increase in versatility (Heal ability is underpowered, however, and that means that changing from a vampire-like ability to heal is not really that great an increase in versatility. Especially since it is a one-way transformation). Now, if Convalesce costs
the total cost for both Guardian Angel and Archangel would be one less than their normal cost. This accounts for the fact that you need two elements (normally a -1 cost reduction) so I think that would be perfect. For those concerned about an Angel Rush, think it thoroughly and you'll see that Gargoyles are better, faster, possibly more resilient, cannot be used to heal and are subject to Eclipse.
