it would be better to limit the mana to 1 cast
Yes, that's true, but first, we need to decide what spells he will have besides stealth, poison, and ammunition theft (although these three are abilities, not magic). What have you decided? Because I must admit, your mercenaries are currently the most interesting thing on the forum.
P.S. Are they for NCF or RTF?
Added 7 minutes later
Oh, I wanted to ask you, fktifzobr@mail.ru, couldn't you add some kind of combat machine, like an onager or scorpion (although the scorpion is more suitable for the fifth level), to the 6th or 7th level mercenaries? I really need a combat machine model for the mod, and I don't want to use a painted ballista.