I think a food guided rudder is an excellent idea. Manatees have been living off the public trust for years and it is time they earned a living. A head of lettice on a pole mounted to the front should be sufficient. As long as the line from boat to manatee is attached in a humane manner, it should work nicely.
On the serious side, it all depends upon conditions, even in a longer/more stable platform. Wakes, waves, wind, tides/moving water, etc. can really affect one’s ability to take photos and control the boat at the same time.
Solo photography is pretty challenging. So much so, that I’ve mostly save my photography sessions for those days I’m out in a double with someone who is more interested in providing a stable platform than they are in long draw out paddling sessions. It can be done, but there are some things that really help.
I won’t use the word that begins with ‘sp’ and ends with ‘s’, because bad things happen when I do, but it kinda rhymes with monsoon. So I’ll state it this way. A pontoon system will work on most any boat. A single paddle mounted to the boat with straps and a paddle float on either end works (on my kayak), as would a more formal system with a custom frame for holding a single or pair of pontoons. This will affect propulsion, but not all that greatly. If placed properly, a normal kayak stroke can be made (if the hull line is long enough for a full stroke).