This implies either that Jesus wrote the inscription on his cross, or that those who wrote it used his language for his convenience. I do not find either of these conclusions very likely.
You forgot the third conclusion.
Our western system of law descends from that of the Romans and part of that western system requires that a person charged with a crime should know just exactly what he is being accused of in a language that he can understand.
It was Roman custom for one charged with a crime to have their crime read to them in their own language, and if sentenced to death by cricifixion, then the crime they were convicted of was inscribed on the cross in their own language. Unless you are going to say that Jesus spoke to the people in Latin and Greek, then by virtue of the inscription on the cross, the Romans were acknowledging that the language he spoke was Hebrew -- not Aramaic.
The second language, if different from the first, was to be the language of the local people so that they also would know why that person was sentenced to death. That language in both cases here was Hebrew -- not Aramaic.
The Greek language was also used as it was the more universal language of the empire for foreigners and visitors to understand. And the Latin was for the Roman soldiers and government officials to understand.
The absence of Aramaic on the inscription speaks volumes. Jesus spoke Hebrew and the Jews with whom he spoke understood it. The inscription on the cross proves it.