@pOke: Dang. Nothing cements my knowledge that I have no coding knowledge like trying to decipher a simple spell like this. :<
I was following you up to a point... But where do you get Load_MaxIndex (& the other "Load_" variables)? And what are they set to? Why's the Index 2?
Apparently it works, which is all that matters (gonna have to check that out myself, actually; might be quite useful). Good on ya for helping Hermit out.
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@Hermit: Hm. So in answer to my question,
"YES, the loaded unit needs to turn to face attackers (as well as attack/cast with animations)". That makes things harder, but not insurmountable.
Something I was working on might be applicable here. I don't think even
my version of this is perfect, but it's a Work In Progress.
Basically I have a spell that allows a Troll to "climb" a tree, becoming an invisible sentry/hunter. I did this by having him 'turn into' an entirely separate custom unit; one that is exactly the same as him but flying & no pathing & no motion (& invisible & such of course). Then, when he's summoned at the target location (a tree), he appears right in/on-top of it (fine-tuning the flying height to match, of course). So now he's in the tree, but as a (flying) unit he still has all his animations, can attack, etc.
So if you hide/replace/morph the Loading unit with a copy of himself except flying/no pathing/motion, create/build/move/place him right inside where the tower is and Presto: a "loaded" unit that is visible & can still attack & cast spells, all with his animations.
Of course, since you appear to have something working this is kind of a moot point (though I think mine might be simpler?...). Glad you got help either way.