Ok,

so there is no something like this for sprites:

c_move (me, vector(2 * time_step, 0, 0), nullvector, GLIDE);
ent_animate(me, "walk", walk_percentage, ANM_CYCLE);

but it can be if I try to simulate a sprite through 3d model by not using Z axis.

I suppose that`s what you mean by "Using a new created sprite as 3D Entity, and use it as target map for the Oldschool bitmap"?

Would be interesting to see how it works. I`ll try that.
Sound easy but could be some geometric problems, ha? We`ll see.

For the panels, I thought of that but I`m not sure if panels has collisions?
Or other properties needed for proper handling.

And for STRUCT, I think it will be like that at the end of the story.
Good old structure for good oldies.

Anyway, thanks for the clarification, mein freund

At least I know from where I can begin.
It`s very overwhelming at the begining.