DIY: Looking for an outdoor chassis as basis for a future project (maybe ;-)

Here is a lawn mower platform which looks interesting on the first glance: http://www.instructables.com/id/Arduino-Autonomous-Lawn-Mower-as-CutFlower/

Here are some platforms provided by robot shop:

And finally, there is an RC rock crawler which seems also interesting: http://www.rcrockcrawling.com/product_info.php?cPath=47&products_id=1390