Loads of Six Flags parks do this - but our park would need to make HH a "true" second gate attraction. AKA tickets for about $20 more than standard admission, and a separate season pass.
So basically, you'd likely pay the same amount for your season pass now without the waterpark, and would pay more for the "upgraded" pass. I do think the park will go this direction in the near future, it makes sense to up the price to $10-15 per ticket and only give waterpark access to Gold members.
Top 5 wood-5-Goliath 4-Ravine Flyer II 3-Phoenix 2-Voyage 1-El Toro
Top 5 Steel- 5-Velocicoaster 4- Maverick 3- Fury 325 2-Steel Vengeance 1-X2
Coaster Count: 444