How can I make product suggestions to TLG?
There is the LEGO Ambassador program too: http://aboutus.lego.com/en-us/lego-group/programs-and-visits/lego-ambassador


  The mission of the LEGO Ambassadors is to work together with the LEGO Group in all areas which concern the worldwide LEGO community and be the voice of their respective LEGO User Group towards the LEGO Group. 


This means you should contact a LEGO User Group (preferably one in your area) and try to raise your suggestion to the group's Ambassador.