So the best possible way I can think of to do this would be as @Deltakosh and @sebavan have suggested.
In Blender take your asset and make sure that your geometry is positioned according to how you’d like it in the final scene relative to your pivot point. There are a TON of different methods on how to do this, but here’s a quick one:
Start with a plane to represent your ground with a position of (0,0,0) and then add your mesh to the scene…for this example I’ll use a cube as our “mesh”.
Note that the pivot point of the cube is perfectly in the center of the geometry.
Ok now let’s move the pivot point to be at the bottom of the cube…we can do this by entering edit mode by hitting ‘tab’ on the keyboard. Also enter wireframe mode in Blender by hitting Shift+z.
How select the all 4 of the bottom vertices:
Now hit Shift + S and select “Cursor to Selected.” This will move the 3D cursor to the center of the selected vertices.
Now go back to object mode by hitting ‘tab’ again. Under the ‘Object’ Menu find ‘Set Origin’ and ‘Origin to 3D Cursor.’ This will move the pivot point to the location of the 3D cursor which is at the bottom of our cube mesh.
When you do this, note that Blender automatically adds in an offset for the mesh’s position so that the mesh has now basically “moved” without you realizing it. I know that’s a tricky concept, but because your pivot point (or origin as Blender calls it) has moved, essentially the entire model has moved…then Blender “moves” all of the vertices of the geometry back to where they were before…essentially moving the entire mesh to line up with your new pivot point.
So if you zero out the Z value the cube will now pop up to be even with the ground plane.
Now when you export that model it will have a position of (0,0,0), with a pivot point even with the ground plane.
Then in Babylon all you need to do is map the mouse movement to the Y rotation of the mesh and I think that should accomplish everything you need?
I hope this helps!