I have drafted business plan, but I need someone to critique my business plan and model to expose any weakness that haven't been thought of, and advise accordingly.
Yes. I can provide that for you. I operate a consulting service doing just this. There are often a number of factors that are missed and thus strategy, focus and execution are often flawed. You are doing really good by simply acknowledging this and seeking advice upfront.
With that said, don't spend too much time on the business plan itself, instead develop it, move on the marketing analysis and plan for execution.