I think you have the right answer but for the wrong reasons.

Certainly 1-2 volts IS enough to produce a usable light-- you can build a flashlight using an incandescent bulb that will run off 1 AA battery (or several batteries in series to produce more amps) at 1.5 volts and I see no reason to see that as a lower limit.

However, the real problems in lighbulb manufacturing occur elsewhere. Generating an electric light requires a very specific set of technologies which copper-age civilizations simply would not have had. Most metals, for example, are not useful as filiments in electric bulbs. Creating filliments of tungsten metal is well beyond the metalworking capabilities of ancient cultures. Tungsten is needed because of its high melting point, and the fact you can get decent resistance (needed to produce heat), light (due to it glowing) etc. Tungsten isn't the only possibility-- one can use platinum or carbon but the light output is considerably less and carbon, particularly, has other requirements due to oxidation potential. However, for a low-voltage bulb, I cannot think of any substitute for tungsten.

Add also the necessary glassworking skills to make a light bulb..... Incandescant bulbs are basically vacuum tubes with filiment inside. The vacuum prevents oxidation (particularly important with carbon-filiment bulbs) and thus increases the life of the light. If you can't make a glass vacuum tube, you can't make a usable lightbulb especially when tungsten is not an option.

The final issue has to do with the load characteristics of the Bagdad battery. While it is POSSIBLE that one might be able to get sufficient current (mA) to power a modern light bulb, I think this is somewhat doubtful. Current is needed because the current is what heats the filiment up and creates the light. Now, this could be worked around by putting many batteries in series, but still low-voltage incandescant light-bulbs are out of reach due to the factors mentioned above, so......

I would say rule it out too, but for reasons of metal/glass-working capabilities rather than voltage.