If the MAXIMUM size is 48"*48", could I have a robot that is 67.88" long if the ends are pointed at 45 degree angles? My logic is that this would still fit within a 48"*48" square along the diagonal
5.65ft wallbot is nothing to sneeze at. I don’t like where this is going. 
Interesting thought. You should be correct. However, I would want a 14-foot wallbot in order to break the game (that was my first thought upon looking at it). I don’t know how effective that size of a wallbot would be.
A bot that expands in all directions like a diamond that gets in the opponents way might be kinda good?
Each corner should be able to retract to allow teammates to pass
Would that fall under a solely defensive robot though?
You could have a long tentialy arm thing that grabs cones 
You are not alone. I really wanted to see the mythical 4-base wallbot realized now that we have 12 motors. Next year, GDC please…
I cadded a wall bot that expands that big and is really durable
The best wallboard strat has got to be blocking the other team’s scoring zones. It would probably still be legal (64 inches to cover, 48 Inch wall; with strafe it could work).
So kinda like kiwi drive logic?
The stationary goals in the middle of the field would make it so that you could only really deny access to a single area of the field