...Seems to me that Barry's comment only applies if the ACC circuits are set for latching---one press for on and one for off. If they are set for staying on only when button is pressed, I don't see why it shouldn't work.
Note that this method would require 2 ACC circuits per switch. Traditional switches with the spring-loaded return-to-center manual lever controller have what amounts to a "center-off" position when no power is applied to either motor/solenoid of the switch. The ACC circuits in a TIU only have a single relay which will apply power to one side or the other; that's the basis of the first bullet restriction about switches that turn themselves off.
Each SW circuit in a TIU has two internal relays which allow power to be applied to one side, the other side, or neither side. And it has built-in timing to only momentarily apply power to the chosen relay.
So in theory you could kind-of-sort-of control 5 additional traditional switches using an AIU's 10 ACC ports with the somewhat onerous caveat of only using the momentary ACC button and the different menu path on the remote.
To dig a bit deeper, to deal with the timing issue when using an ACC port, there have been occasional threads about methods to limit the amount of time an ACC port is left on. The classic example is an uncoupler electromagnet under ACC control. In this case, external circuitry is used to guard against leaving the ACC output latched (left in the ON position). Similar guard/timing circuitry could be used for the switch application. It wouldn't be expensive (maybe a few dollars per switch) but you'd need to be a hard-core DIY'er with lots of free-time!