What if?

[Joseph_21sv]

That would be TTL and CMOS address decoders (2-4, 3-8, 4-16, …), which could have been integrated into a single circuit for that application even as early as 1973.
In addition, since a dual design could have simply been two copies of a pre-existing design in the same computer, it might have been a machine programmed by nothing but sixteen toggle switches with no real video or sound driver, just sixteen LEDs and 256 words of memory. Of course though, most pre-existing designs used real video (and sound) drivers and thousands of words of memory, even if what video (and sound) they drove were a 1-bit display limited to strictly text, that excluding semigraphics and even lowercase letters for the font could have had only 64 characters or been too blocky to be able to distinguish case or have use for semigraphics (and one channel with fixed sound effects). Since the design would be doubled, the resulting machine would have double the capabilities of the basic design.