I worry that the maximum income multiplier would have distortive effects. For example, if all my employees make high salaries, I would have a strong incentive

I worry that the maximum income multiplier would have distortive effects. For example, if all my employees make high salaries, I would have a strong incentive to hire a company that provides janitorial services, rather than hire a janitor in house. (Which is presumably more efficient, as most firms do that in the current structure.)