A toy train going around on the floor of an accelerating rocket probably looks weird in some frames, because of frame dependent forces. We just need to understand forces, then everything will be quite simple. What you said does not sound simple enough.Do you think video IFR and train FR behave the same way, i.e. constant transverse velocity ?
I think train FR has reducing transverse velocity thus changing video IFRs to smaller velocity one as its instantaneous IFR.
In video IFR, the right ward moving train against the rail on the floor with same velocity with video IFR is at rest at a moment but train is climbing up slope of the tilted floor with relative speed against floor. Next moment train reduce right ward speed by transforming kinetic energy to gravitational potential energy. Does such a conjecture work?
If we managed to understand a moving lever with two rockets attached to its ends ... that would be great.
I remember to have read somewhere an interesting special relativity "paradox" considering two perpendicular rods $A$ and $B$ of equal proper length $L$ fixed at point $O$. In the "rest" frame equa...
My point is that there is something to ponder about forces.