Let's talk about our Red Rush strategy...

the red player can attack the blue player on the 1st day of the week with a purchased reinforcement, but in this case, the stacks containing units purchased this week do not participate in the battle (skip their turns)

There might be some nuances here that would be worth considering...
Example 1: Red enters the blue player's territory with a maximum speed of 9 units on day 7 (let's say the blue player has a speed of 11), and on the first day of the following week, they receive reinforcements, let's say, dragonflies, and attack the opponent's main hero. The dragonflies will skip their turns, but they will still provide the initial speed boost...
Example 2: Red receives a couple of immune creatures from the reinforcement on the first day and attacks a hero who has Armageddon and enough units to eliminate everything in 2-3 turns...
In other words, the mere presence of a certain unit on the battlefield can radically change the outcome of the battle.