Suppose, for a minute, that you had a deterministic simulation of a human brain (perhaps involved in a debate with a simulated physicist). When the simulated brain vehemently insists upon having free will and making meaningful decisions and having the feeling of freedom in his heart, are you going to disagree with it, in the face of the fact that all relevant information processes are identical to a real brain?
I am not sure what you are trying to say with this, as its begging the question. I could just as well say the following and it would be equally empty in persuasive value...
"Suppose, for a minute, that you had a human person with free will (perhaps involved in a debate with another human person). When the person vehemently insists upon being determined and only having the illusion of making decisions, are you going to disagree with them?"
I am simply adding determinism in the most explicit way imaginable, from the outset, and showing that you are still stuck with the same problem.
In other words, the simulated brain is making choices, decisions, and feeling free will in his heart, just like a real brain. Yet determinism is 100% manifest from the beginning (we could even run time back and forth in the simulation and watch him make the same decision over and over, like a movie, if we wanted). In this situation, you must in some way reconcile the fact that 1) the simulated brain very definitely percieves free will and 2) we have "hard determinism" by assumption.
After you have reconciled these in whatever manner you like, I simply claim that you have also reconciled "real" determinism with "real" free will, because there is no way to distinguish between deterministic laws of physics and an arbitrarily accurate deterministic simulation from inside.
To me, the whole thing seems very easily encapsulated by noting that free will is exactly the self-perception of performing calculations which control future actions. Free will is very real -- I am percieving it right now. And my decisions are also very real -- I am making them right now. And they get along just fine with determinism.