Here's my opinion:
They should have made Brauner a unappreciated human artist who dabbling in dark magic with the intent of enhancing his artistic talent, but ended up turning himself into a vampire who now desires to wipe out humanity for not appreciating his artwork (cheesy I know). Decides to use his art and now found power to steal Dracula's power.
The sisters should just be two of his victims (no need to save them).
Death should still be trying to eliminate Brauner.
Get rid of that whole whip draining away the life of non-Belmonts who wield the whip.
Neither Jonatan nor Eric should be dead. We don't need the priest. It would start out with John and Eric investigating the fact that Dracula's castle has reappeared and seems active. Tehy hit a snag and realize they can't do it and decide to regroup at the entrance when John's son Jonathan shows up with Charlotte. Jonathan and Charlotte decide to finish what John and Eric originally set out to do. At which point, John and Eric decide to stay at the entrance and provide support anyway they can. John provides quests (more interesting than the ones we are familiar with) ending with acquisition of the vampire killer (no power unlocking needed) while Eric sets up shop. Both of them offer advice from time to time.
The Vampire killer whip is the most powerful weapon of the game for Jonathan.
Death will not be in a set boss room because we will be constantly searching for Brauner. During your first encounter with Death, he simply tells you not to interfere with his mission (which is to get rid of Brauner and revive Dracula, the true master of the castle. He doesn't tell you this though). In every subsequent encounter, he will fight you and if you can't defeat him fast enough, he will run away. If you don't defeat Death before fighting Brauner, you will have to fight Dracula and Death at the together in the throne room after Brauner.
This is my vision of how the game should be.