Welcome to my world! I was looking for the same thing 5 years ago - I may almost be there.
Tubing fun diminishes when the tow boat is over 27'. Older kids like an aggressive tubing ride and longer boats just can't turn tight enough. We use a waverunner now for tubing. My 32' works fine as a ski and wakeboard boat. I'm re-rigging to bravo XR's (going from surface drives) and should gain a little low speed manueverability.
The need for speed does make watersports a little more difficult also. You're going to need strong drives that can take the kind of launches you need to pull up a skier.
Now that I have the 32 I would not want to go shorter - I like the better ride in rough water.
Maybe the boat you are looking for is out there, but you may need to lower your expectations regarding either top speed (90 - 100 mph) or family towing fun. Good luck