As you can see it's not quite as simple as that. Many uses of γινομαι have
the sense of coming into existence, being born, being created or being made.
This is especially the case in the creation account. The idea is that light
did not exist and then it came into existence. See the first chapter of
Matthew where we see the genealogy of Christ. The verb used in γινομαι in
every case.
So the question is how the English idiom expresses this thought. Do we say
stuff like 'Let there be plasma screen televisions' or 'Let there be Dyson
hoovers'? Do any of the following represent good idiomatic English?
Let light become
Let light come into existence
Let light be made
Let there be light
I quite like your vocative suggestion:
Light, be made!
But I'm not sure if the Hebrew conveys such a vocative sense.