In Reply To #18
This isn't necessary. I don't remember which castlevania was, but i think it was CoD, death wasn't weak against holy. So their weakness doesn't need to be necessary their opposite element. It could be like galamoth from symphony. Galamoth was weak at his head. You could fight a boss and do minor damage to him, but with the appropriate weapon or item and the right spot to hit you would be able to defeat him. Otherwise you want be able and you'll have to go and find that weapon or item to defeat him.
So with that element, the game will be more interesting, harder to defeat and specially if it has secret bosses that you will encounter random at certain places or under special conditions. If you want be able to defeat them you'll see game over, but that will add a new experience to the game. I know that it will be annoying, since you'll lose all the progress that you have made up to this point, but this will give extra life to the game and also it will be interesting searching to find all the secret bosses at the game, specially if they play role at the ending of the game!