If you think "change an eyeball to a hit" is an independent, always-on ability, then so is "You cannot perform another attack this round." So if you're going to treat the three sentences as independent always-on abilities, you never get to attack. To quote one of our favorite kids' movies, "I don't think this plan was thought through very well."
The first part of the ability specifies when it can be activated; the rest describes what happens when you do activate it.
For the record, I came up with the question, doctormungmung just posted it, so to the extent that it's a stupid question, blame me, not him.
Also, I agree with Buhallin's reasoning, to a degree. Because the third sentence says "another attack," it does allow for the ship to make an initial attack, because in order to make another attack, you have to make an initial attack.
So, while I think this approach (mini-focus only applies to the additional primary weapon attack triggered by the miss on the intiial attack) is correct, I don't think the card does a very good job of limiting it that way. And yes, I understand that there's only so much room on the card, blah bah bah, but the issue could be corrected by inserting "then" into the second sentence as Duraham says, or through the use of semi-colons.
I don't think it's a stupid question. I at least understand the reasoning behind it--unlike, for instance, the perennial confusion over how to treat the damage done by an ion cannon.
But that second sentence has to be read in context. As dbmeboy pointed out upthread and you've acknowledged, the third sentence is clearly dependent on the first--which means that it's a stretch to assert that the middle sentence has anything other than the extra attack as its implied antecedent.
And further clarifying it in the ways that've been suggested might have associated costs, too. If the card said "You may then change…", that could be read as (or, at least, reasonably confused with) disallowing any intervening effect--like, say, a Target Lock or Han's pilot ability. You could assert a closer relationship between the first sentence and the second with a semicolon, but that assumes that your reading audience understands and correctly interprets the meaning of a semicolon. You could say "When you make this attack, you may change…" but that probably is too much extra language to fit on the already-cramped card. And so on.