The way in which Starmada point costs are determined (multiplicative rather than additive, with that pesky square root involved) means that there is no reliable way to have 'swappable' components without re-computing the entire point cost for each configuration.
That's a cop-out Dan
I like Noel's idea, of adding a "Swappable" special ability which flip flops the "load" of the weapon.
and to point cost it, you would use the same formula as you have now. But give swappable a .75 multiplier. with the limitation that you can't have a swappable weapon that uses a special ability with a multiplier less than 1.
What it amounts to is a limitation in the weapon rather than a "value-adder". In other words, imagine, if you will,
1/1/1 extra hull damage/ignores shields/swappable
Normally, I would use the ignores shields AND the repeating abilities simultaneously, however, I must now choose between the two. Thus I am less effective than the weapon as a whole, but somewhat more flexible. And it allows you to model the hot swap loads of various missile systems.
jim