I mean I think it would be. Easily defendable. Great location for trade. Close to Persia/the rest of Asia. Pretty much all the same reasons that Constantinople was one of the most important cities in the world for over 1000 years. But it seems like it was sort of a backwater until Constantine picked it to be the location of his New Rome.
In the run up to the Roman rule in the East Byzantium was indeed a significant city. mainly due to the control it had to the access of the black sea.
In the conquests of Philip II, the father of Alexander the Great, he besieges the city as a way to put pressure on Athens. This is important to Athens as most of their grain to feed the city came from the black sea and lower Don. Therefore an enemy so close to the trade in the form of Philip and the Macedonians put pressure on them.
During the Roman Period and the republic and empire, Athens was still an important city yet under the rule of Rome it meant trade and grain was coming from different areas. Primarily Egypt and North Africa. This shift negated the role that the Black Sea grain had, and thus this trade route became less important.
A Good work to read for the Macedonian Wars to gain an understanding of the importance of byzantium early on would be 'By the Spear' by Ian Worthington.