Might I just add that Paint Shop Pro 7 (or 8, if you're feeling adventurous) is by far the best bet.
[...]
This is going to turn into one of those "My graphics programme's better than yours" threads, isn't it? I can see it coming....
MINE IS BETTER! MINE IS BETTER!!!
*cough*, *cough*, Just kiding. [I know PaintShopPro, but can't find a crack... ;D :-X - Does it have a paths tool? Ok, it's off topic, I know]
About the constant rate of fire.
Indeed, the invisible target does compel the unit to fire constantly. But it won't target anyother units unless the invisible one gets killed (which is impossible with the available addons; besides, if it is destructible, then the AI shooter won't take too much to eliminate it; therefore, bye bye constant rate of fire)
. Or maybe if you change its 'cost'.
But why would you wan't the AI unit to fire over an inv. target? Is it for a cut scene?
Or do you wan't to create a 'inbattle' usable script?
Such as a base-of-fire simulator.
If you need the first one, then there's no other choise than using an addon (I think! Look that some BAS missions have choppers firing constantly, and I don't know if it's over a inv. target or if it's just a script...)
If you need the second, then it gets really complicated. Base-Of-Fire is something we've been expecting for in a script... I don't tell you that it is impossible, but, in my opinion, it would still involve an addon.
For example, if you want a BOF, you need a high dispersion mgn (look at JAM addons). Then designate a target to the mgunner. It will fire constantly, but it will miss the target often... which means that it will take some time to hit it. So, as the real BOF consists on shooting constantly over areas with high probability of enemy presence or hard detected enemy presence, this simulation would fulfil such need, mainly if you use the invisible target addon as a virtual target area.
But details will come after your answer...