The main problem I see with the mesh fencing is that you will, with almost 100% certainty, not keep out the bass/crappie. Either they will make it over in high water, or fingerlings will pass through the net and grow out to a size where they decimate your "protected" FHM population.

I agree with snrub, remove as many small bass and small (or all) Crappie as you can and stock advanced size forage. I would include some brooder sized GSH, although depending on an accurate assessment of your current bass population they may also end up as snacks.

The wisest decision (but not necessarily cheapest) would be to have your pond shocked to get a more accurate look at what you have, then formulate a plan based on your ultimate goals.