The Defiant is my favorite ship in Trek!
What I would have done is copied the Hasbro Millennium Falcon.
Make the Defiant for the Playmates 5 3/4" figures (basic carded size the largest portion of the collection is scaled to - just like that Enterprise D bridge playset you were discussing).
Have the top of the toy vehicle come off - just like the back of Hasbro's Falcon - and have the interior be the bridge of the Defiant. If there's room, a back part of the ship could be engineering or a shuttle bay with a underscale 1-figure fitting shuttle pod that "launches." But at least you get the Defiant's bridge inside the toy that matches the exterior.
Maybe "EU" the ship a little and offer seatbelts like the Orinoco toy had so that you can "fly" the Defiant upside down in battle and not dump the crew out all over the place.
Then make a Jem Hadar fighter ship!
Thank you for seeing how worthwhile is DS9. The DOMINION WAR will never be forgotten.
Screw Berman. DS9 was all Ira Steven Behr as the Executive Producer almost independently in charge. The man is a genius! He was with DS9 from the start pretty much, but he got control by 3rd season and you can see the difference it made.