I am a Viper owner and I love my boat.
But as a fellow sailor we owe you thoughtful responses to your criteria.
1. Trailerable (can setup in under 30 minutes). The Viper is very trailerable. It is 21' long and very roomy for 3/4 people but only weighs 750 lbs with mast and rigging. So it tows like a dream.......BUT.......if you are going to keep it at home and put the rig up every time you want to go sailing, then it is going to take you more than 30 minutes from the time you arrive at the ramp to the time you sail away. I speak from experience because I keep my Viper in my drive way and I drive to wherever I sail, so I have become very proficient at rigging and launching my boat.
The Viper is probably the easiest and fastest of the 20 ' sportboats to rig and launch because (a) It has a light carbon mast - one person can lift, 2 can do it quickly. b. The rigging is very simple - just uppers and lower shrouds to click into the hoop shaped chain plates - no jumper stays, no check stays, no back stay etc etc c. No roller furling jib to mess with (d) Slot in the foredeck, so the mast just gets tilted into position quickly. (e) The keel doesn't require a hoist, just uses a line from the spreaders.
I doubt there is a faster sport boat to rig. But, not 30 minutes. My crew and I are a smooth machine when we pull into a regatta parking lot. We each know our role. If we go flat out (as we had to recently when we arrived late ) from the time we get out of car, until the time the boat is tied up at the dock with the jib hanked on forestay took us 45 minutes...and we are faster than you will be.....and we were really rushing. Do I think we can break 30 minutes if someone laid down a challenge with a cold keg involved ? Probably but on an everyday basis it is going to take you and your 2-3 casual friends an hour or more to rig any sport boat and launch.
For you requirements of a ramp launched boat that you and your friends could take a quick spin on an impulse on a Saturday afternoon, I wonder if you should be thinking about a simply rigged modern dinghy.....like a Laser 2000.....rather than a keel boat. There are some relatively stable dinghies out there...they might not have the self righting characteristics of a sport boat but they are very manageable.
Sure, on a windy day, your Laser 2000 or other similar dinghy might risk capsizing when a Viper would self right, but both boats are going to be a handful on a windy day and both boats are going to be easy on a quiet day. Viper can fit a lot more people but its going to take longer to rig any way you cut it.
Viper only draws a few inches with keel up for launching, and getting out to end of dock, but once you are sailing it draws 4' 6"
$15,000 gets you a good quality dinghy in the used market. $15,000 doesn't get you much in the way of a modern sport boat.
On all your other criteria, the Vipers scores a perfect 10. I'd love you to become a fellow Viper owner but I wouldn't want you to join us and then be disappointed that it doesn't really fit your criteria. Take up that offer to sail a Viper but also check out a couple of dinghies.