[Den-O]

The show was revamped but trust me they don't design new toys halfway through a shows cycle like that due to poor ratings or anything else. The introduction of Tategami LiOh was always going to happen. Generally all DX Sentai toys have at least a tab or 2 that doesn't get used in the final design of the toy. Just vestigial elements like how humans have tail bones.

As for that minipla that's where the mask for Go-Buster Oh goes. When the Rabbit is in copter mode the standard storage for the mask isn't usable because the legs fold up. So you plug it on the blades to make a small second set of rotors. That has nothing to do with a combination that never happened.

The plot may have been altered but I doubt it was very significantly. At the halfway point there isn't alot that can be done to change things up outside of new stock footage scenes and monster of the week type stories. The overall plot is pretty locked in by that point. Remember these shows are planned about a a year and half to 2 years out.