Mechanics a particular entry in a series used that you wanted to see used again?

So in Castlevania Bloodlines, two mechanics that are really fun and just pretty cool are seen that I wished another Classic-vanias would have used:

1. John can used his whip swing from ANY ceiling, unlike SCV4 which allowed swinging from specific points. And not only that, during that swing, John is totally invincible and his body becomes a hit box. So it can actually be useful and it makes traversal pretty fun.

2. When John or Eric max out their weapons, they each get a special sub-weapon that can decimate enemies and many bosses. In the case of John a stream of water that chases enemies and deals multiple hits. What's the catch? If you get hit you lose it and the final upgrade to your weapon. Which i think is fair and a pretty cool mechanic, you want to use the extra damage and busted sub-weapons? Then you gotta be careful.