This a very sweet and cool design, it is nice to see this theorical idea applied to a real use case. I think it should be demonstrable that for a turing machine, for a size-bound input state space, there is a data bus width (with matching eprom and register) for this kind of machine, so that it emulated the said Turing machine. Also, the eprom is a non-invertible function, but there again is always a wider bus, register and eprom, this time with a reversible (injective) action, that would have, nontrivially, equivalent behaviour. In this reversible case, the action of the eprom could be expressed in terms of a unitary transformation acting on a quantum register, so the traces of the register values against time would be a subset of the valid quantum state dynamical trajectories. In this case the two I/O chips below are not required, and the system would evolve autonomously after an initial state. So look, this computer is a cousin of a quantum circuit.