Ok just checked through and pretty much everything I have works with this new code, bravo! (and bravo unit tests!). The two exceptions I found were:

1. frequency_response raises an error with LinearICSystems.

sys = ct.interconnect([ct.ss(ct.drss(3,1, 1, dt=0.2), inputs='e', outputs='u'), 
                       ct.ss(ct.drss(3,1, 1, dt=0.2), inputs='u', outputs='y')], 
                      inputs='e', outputs='y')
sys.frequency_response(22)

raises
StateSpace.__call__() missing 1 required positional argument: 'x'. No error is raised for sys(22).

2. In constructing this code, I encountered the bug that that drss cannot take named signals using the 'inputs' keyword. sys = ct.drss(3,1, 1, dt=0.2, inputs='e', outputs='u') raises rss() got multiple values for argument 'inputs'. Not sure if this is new or not.