If you are only going to fish the bays, I think this would be fine. I imagine that it would be fairly stable. It might not be the best idea to try taking it through the surf. The trolling motor probably wouldn't get you through the surf and using an 8' paddle might make it a little hard to control.
Most kayaks are rotomolded polyethylene and some are stronger than others. It depends a lot on the hull thickness and shape. I would suggest a test paddle before making any decision to buy. Get on it and see how much the hull flexes. As long as you stick to the flat water it probably isn't going to matter.
There are lots of kayaks makers and there are a number of shops that will let you take a test paddle. You might want to check with some of the more established brands (Malibu, Ocean Kayak, Cobra, Hobie and Wilderness Systems) before trying something from a smaller company. The odds are that you might find a kayak that suits your needs from one of the industry leaders. They all have multiple fishing-specific kayaks in their product lines. Several of those companies have nice wide kayaks, with 550-600lb. load capacities kayaks specifically designed for larger paddlers. They are very stable and have lots of fishing friendly features.
Just remember: choose a kayak/pontoon boat that meets your needs. The important thing is that it gets you on the fish, not what it looks like. If you need the X-Wing to fish for bass in Mission Bay; go for it. Of course, the kayak purists will give you lots of crap........
Try as many as you can and get what works for you.
http://www.malibukayaks.com/
http://www.oceankayak.com/kayaks/angler_editions/
http://www.cobrakayaks.com/kayaks.html
http://www.hobiecat.com/fishing/index.html
http://www.wildernesssystems.com/category.asp?id=5
http://www.oeexpress.com/kayak-sales.html