I dind't use the 2011b version of Matlab for model export but I think that the process I'm suggesting will work anyway.
To change gains you have use the multiplication block and a constant instead of the gain block, you'll see that the constant will be recognized by Veristand as a model parameter and it will allow you to change it in runtime.
For the saturation you could use the dynamic saturation block with the constant as mentioned above.
In regards to the integration I don't know what you want to do, you can reset, specify the initial condition, again, with a constant, and that should to the trick.
Let me know if this helped.