Hi, @Cedric:
First, let me thank you for your time and advice.
Of course, I’m still a bit reluctant to go the Physics Engine way. All this is, definitively, something that I thought could be done easily with the basic collision functionality (is just a grid with bounding boxes) but finally is costing me a lot.
I have another thread on the forum that initially was opened for a different issue, but ultimately has come to this very same subjects. Maybe you can be so kind to take a look at it, and review my last shared PG there.
Best regards.