Now we are back at square 1!
The ex-Saxon regiments were NOT fusiliers, nor were they grenadiers; they were musketiers.
At that age, it was the internationally accepted practice that the senior-most infantry regiment formed the right-hand unit of the line of battle; on its left was the next senior-most regiment etc, etc.
Given sufficient warning of an action, this deployment took place before every battle. The junior regiments just had to fit in as best they could.
It is of interest that FtG formed no new infantry regiments of the line during the 7YW; he did raise many Freikorps, often of infantry, cavalry and light atrillery, which were specifically used for scouting and skirmishing.
IR Nr 49 was the last line regiment raised prior to the 7YW, being raised in 1742.
IR Nr 50 was raised in 1772, the others later.