Take the zipper, for instance; it has sets of 2 cars around a track. It would rotate, load 2, rotate, load 2 and keep going until all are filled. Sometimes, flat rides are inefficient. That's why you have four loading zones at WDW Tower of Terror and 2 drop shafts. That's why Star Tours has 6 simulators and mission space has about that many.
I think the radius for sure should never stop moving and guests should enter the cabin as other guests are leaving. The coaster Ferris wheel I'm not sure about. I'd have to check up on how that one boards; a good reference would be the Disneyland wheel that it's based on.
Many dark rides are omnimovers like Haunted Mansion and Spaceship Earth, and even many coasters have non-stop stations like Rip Ride Rockit, WDW Primeval Whirl and Alton Towers Spinball. In real theme parks, not every ride can completely stop to board. Many rides have to load guests while unloading guests. That's just how they operate.
So this is an important feature to get right since it is more than just ferris wheels that will have non-stop vehicles (chairlift rides too...).
And one last note: when I mentioned how many parks put multiple flat rides to increase capacity, I tried doing that in my park. I put a sky ace, and it got such a long line, so a put another on the other side of the path, but because I couldn't join the queues into a single line, they BOTH have long lines when it would be better just to have a single long line and have the two rides run opposite each other (one loads/unloads while the other does the ride cycle and vice versa). I tried this with two adjacent magic twirls and same story.
We definitely need to be able to merge queue paths into a single queue if the rides are the same; that will really increase capacity and save park real estate by not building two separate queues for the same type of ride.