Hi Mike,
I have a little different perspective on using a pontoon on a river. If river fishing is your primary way to fish I think you may be wasting your money on a standing platform and bar. It is probably a great way to fish on still waters but with a river it just doesn't work for me.
Being able to stand with the flippers on doesn't seem like a plus. With currant you need to have your fins in the water so you can control your drift. You may also have to use an oar every once in a while and you can't do that standing. If you hook a fish you need to be able to move to a back water eddy or at least keep you going in the right direction. You might even want to drop your anchor and again that is easier when you are sitting down.
On a river you might think you could slide the platform in and out as you needed it. That does solve the problem of being able to use the fins. As you progress down the river if you sit down to control the boat and then want to make a cast you still have the bar up and in the way. So we have bar up and then down, platform in then out or using fins and then not using fins. This is just too much going on to enjoy the float. It is versatile in theory but not practical for me.
If I was fishing a lot of still water than the standing platform and bar would be a great asset. But I would also have a trolling motor and that would control the boat, not my fins. I think you need to rent or borrow a pontoon and give it a try. Your experience may be different than mine.
Frank