While being a vampire, you can suck juice from corpses to heal and regain energy quickly. It takes away a lot of difficulty as you can just heal after getting hit and go on your way. 

You can also use it to regain lots of energy quickly. You can turn into a machine gun or swing a sword fast with little upgrades to energy from the Juice fountain. 

Not only that but since 0.1.1, what I would call "Juice Knockback" was removed. Sucking juice from bigger enemies would no longer jerk you around and push you back.

All that makes being a vampire very fun however it takes some challenge away from the game, especially since there is no penalty for sucking juice.

So my idea is to add a form of levels to the vampire, while keeping it fun. Plus, bring back Juice Knockback as a stat. Depending on how powerful a vampire you are, the more juice, health, and energy you gain from enemies. To add, the more powerful you are, the more Juice Knockback you can handle.

For example, a weak vampire would jerk around and lose some of it's free movement sucking juice from a bigger enemy. Meanwhile a powerful vampire would handle them fine.

The best way I think this could possible would be by a big Good Juice Pot just for example.

You would fill the pot with juice to make a mixture of Good Juice. Once you're happy with your mixture, jump in it soaking yourself in it, and wait for Batty to do his thing. The more it was filled, the more powerful vampire you've become after Batty.

I feel a Good Juice Pot is an easy way to understand the levels of a vampire, without using an upgrade system like such of the Juice Fountain. 

Quite bold of an idea, but thought it'd be nice to try putting my ideas out.