I think being the commissioner, you should have the ability to set the % for which a trade can be considered vetoed. 4 players in a 10 team league can run who gets who or who can't trade. Or have the ability to see who vetoed to see if there is a pattern or issue with a team.
Alejo Arrizon commented
I really like this idea to having an option. With 4 vetoes in my 12 team league, trades are very unlikely to occur.
I suggested this 2 years ago. In my 12 team league, 5 votes would be better. Some leagues have family members, etc. and while they should act independently, sometimes I question that they do....