Can Command require possession of the new AGSU prior to the wear-out date of the ASU?

Outside of my initial response, I have to address the elephant in the room. A 1SG is asking this? A SF 1SG is asking this? And the Call Sign? All call signs with the number 6 are for the Commander of the element. The number 7 is for the NCO. Any 1SG worth their weight would know this.

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No, they can't officially make you purchase it before the wear out date. They can certainly unofficially make life very difficult for people who don't get them, however.
It was the same when we transitioned from Class A's to the ASU's.
No one who went to a promotion board or interviewed for a CDR or 1SG position in the old uniform would be recommended for promotion or positions, since they "clearly couldn't be bothered to do more than the minimum, and that's not leadership material".
Quoting the old leadership from back in the day.

Is this question really serious? And coming from someone who claims to be an E8, with presumably over a decade of military experience?

Every old uniform item has a Wear Out Date - which sets the last date that item may be worn as a uniform.

Every new uniform item that is going to be required has a Mandatory Possession Date - which sets the time where everyone who would wear that item is required to own it.

Those two dates are set independently and have little or nothing to do with each other directly, but when the new item replaces an old item those two dates will always OVERLAP.

The new item is ALWAYS required before the old item is no longer allowed to be worn.

Both dates are set by the Army and apply equally to every unit and every soldier.

Units have no control over either date.

In the real world, most units will "encourage" soldiers to obtain the new uniform item ahead of the Mandatory Possession Date, while the unit cannot require a new item ahead of the Mandatory Possession Date we all know how persuasive a unit can be when they really want something.

In the opposite direction, in the real world, some units will strongly discourage wearing an old uniform item before the actual Wear Out Date, and other units may be less concerned about someone wearing an item beyond the Wear Out Date. These depend a lot on what the old item was and, of course, on when and where someone tries to wear it. Most units are less worried about 'field' items worn in the field than about service dress uniforms.

The legitimate case for something close to this question would be during that overlap when the Mandatory Possession Date for the new item has already passed and the Wear Out Date for the old item has not come yet. During that overlap period, you ARE REQUIRED to have the new uniform item and the unit certainly may require you to wear it. The unit cannot completely ban the old item prior to its Wear Out Date, but they can specify the new uniform item as the required uniform any time they are directing what uniform to wear.

DA says mandatory wear date is the standard. Therefore, logic dictates that anything prior to the mandatory date is recommended but not required.