We have begun the process of making a 'Conversion' for our deck to turn it into an arena cos of the lack of events. At the moment its just got a floor but we are going to be swapping the glass in our porch with Polycarbonate to make a driving booth, adding proper low walls using 8"x2" wooden beams and possibly even a pit as it is built on ground that slopes away.
Doubt you could run an event but it would give people somewhere safe enough to test out their machines. Flippers would be an issue though as you would be tossing other robots into the garden. Perhaps a high net will be enough. Binky would also be an issue after what it did to cicatrix and Satanix.
But the aim is to eventually to have an arena you could use for a proper battle!