First for number 3, cause that's the easiest. The autoloader is slower yes, but that doesn't change the actual firing rate of the mechanisms in the weapon, just the loading rate, and the changes to that would be part of the autoloader system having limited loading speed, not part of the weapon itself.
As for your reply to 6, I get that the crew version is lighter, but if you can make the weapon lighter with no performance drop, why use the heavier version?
Now as for the safety of the weapon. Plasma discharge is no joke, even coming out of the front of the weapon that would cause a drastic temperature change in the immediate area. But physics behind that aside. We're talking about mechanics of an infantry weapon (even if it is on a tripod) being able to fire T9 shells. That's literally a potential 8 tier increase in damage, and we can't really have that for mechanics purposes.