I don't believe for a second that Michael Weatherly is even considered by Paramount+/CBS for anything.
Whatever happened behind/off camera at NCIS and Bull (see also Pauley Perette/Mark Harmon and obviously Eliza Dushku lawsuit payout) it was never fully revealed.
That all happened under the lead of a certain Leslie Roy Moonves, who was the CBS CEO until his termination following numerous allegations of sexual harassment, sexual assault and abuse... And if you don't dislike that guy already,
he hasn't had any love for Star Trek either.
Further DiNozzo's character hasn't aged well (see Barney HIMYM) and the whole Ziva/Tony story line kind of reached it's creative end points anyway.
Most importantly - keep in mind - Paramount+/CBS is doing this to keep their broadcast license or whatever down under.
These usually come with stipulations of having not only a certain percentage of acting talent from there, but also production staff and more.
Finally, there is plenty of acting talent from Australian, New Zealand and elsewhere that might like to have a steady multi year job at (close to) home.
I'm not ruling out a famous lead, guest star or crossovers from within the NCIS-verse though.