This is an edited pics in which I duplicated some wheels and stretched the "body" to see how this thing could come out.

Thinking about the suspension.
The idea is to build a couple of pivoting subchassis connected to the mainframe.

Each subchassis wll have the usual 4 links suspension set-up. The pivoting movement AND the 4 links suspension should make the rover copy better the terrain.

This in theory;-) If not I'll screw the subchassis to the mainframe.

After some thinking I started to find a geometry for the subchassis. This is the result in a completely temporary form. The red dot is the pivoting point.
It seems articulation is enough.
Starting to seriously build. This is the subchassis.
With axles monted
8 mm solid bars lower links.