Wade spelled it all out in new court documents, obtained by TMZ Sports, saying his 15-year-old daughter, who is transgender, should be allowed to legally change her name and gender ... despite Funches-Wade's objection filed earlier this month.

Wade argues in the docs it's all in Zaya's "best interest" ... saying, "A court order affirming her identity will allow Zaya to live more comfortably and honestly in all aspects of her life -- from simple introductions and food orders, to applying for a driver's license and filling out college applications."

He added in the docs, "This petition is about allowing Zaya to take on the milestones of being a young adult with confidence and joy."

Earlier this month, Funches-Wade argued in court documents that the move should barred ... alleging, among other things, that Dwyane "may be pressuring our child to move forward with the name and gender change in order to capitalize on the financial opportunities that he has received from companies."

Dwyane called the allegations B.S. in a social media post shortly afterward ... and he expounded on that opinion further in Tuesday's filing.

"Siohvaughn's allegations are libelous at their core, and are, at best, nonsensical," Wade's attorneys wrote in the docs. "Dwyane filed this Petition because Zaya asked him to."