I think the next generation of streetcars we get should have batteries on board. Not a lot, just storing enough energy to get the vehicle through an intersection, or around a curve. We'd only need power caternaries on the straight stretches of track. It'd greatly reduce the amount of support wiring needed, and eliminate the spots where the power takeoff is most likely to lose contact with the conductor. In the event of a power outage, it'd also let the streetcar get to a safe spot before stopping.
The drawback is that the batteries would add weight, and would require expensive DC-DC converters to provide the 600 V needed by the streetcar.