The idea is this:
The Company's commander is a Captain (O-3).
The Company's XO is a First LT (O-2). This position is temporary.
The Platoons' commanders are First LTs (O-2s)
The Platoons' XOs are 2nd LTs (O-1s).
The promotion time to Captain (O-3) is moved from 4 to 7 years. O-1 to O-2 becomes 3 years, and O-2 to O-3 becomes 4 years.
Second LTs (O-1s) will learn the Platoon Commander's job for 3 years from their First LTs. The First LTs will command their Platoons and then rotate to do a 1-year tour as the Company XO. This means that First LTs (O-2s) will rotate command of all the different platoons and serve 1 year each as the company's XO to prepare them for their next assignment as Captains.
The other promotions will be a little quicker instead of the usual 6 years to go from O-4, O-5 and O-6, it will take about 5 years to make O-6 at 22 years.