For me, I plan to use the yak in the following ways:
Launch from public parking areas without being governed by tide. I can be governed by tide on foot just fine, don't need a yak for that
Paddle short distances (up to 2 miles) before getting out and fishing from outer bars and shoals or inaccessible points, necks or inlets.
Sustain sudden wind, waves, and be able to launch and land in the surfline if needed.
Maintain the ability to progress against the tides if necessary, up current. This depends on the spot I guess.
Tether/anchor the kayak someway so it is secure in wind, current, tide, etc - even when there is no dry land available.
Carry goods in dry storage, reasonable quantity. Watertight backpacks are acceptable alternatives. Safety gear, water, lunch, etc.
Get back in the yak even when tide has risen to waist deep. Have a method of getting in even when the water is over my head, in case of flipping.
Mount a rod holder that is suitable for my best rods without concern for damage.
Easy to mount on vehicle, although this is partly the vehicle and rack in play.
I guess it would be impossible to get all of these, so I have to think about which are most important to least important next...