He can be included with players if the salaries match. The Nets sign and traded D’Angelo Russell to Golden St. The Nets also sent Shabazz Napier to Golden St because they needed more salary to match KD’s salary.
Shabazz was a free agent also, not an existing contract. So he was signed and traded with Russell. We don't have the bird rights to any free agents to include with Ayton in a deal like that.