Created a better logic-to-analog proxy approximating output impedance. This revealed some bugs in the code which have been fixed.

Basically, borderline schematics like

    TTL_7404_INVERT(c9f, c9c.Q)
    TTL_7404_INVERT(c9c, c9f.Q)
    SWITCH2(coinsw)
    NET_C(c9c.Q, coinsw.1)
    NET_C(c9f.Q, coinsw.2)

in which the switch connects TTL-Outputs to ground now work. In this case, the addition of an analog device (switch) cause the netlist code to treat the TTL outputs as "analog" and (re)connect all existing and future connected terminals to the analog output. 
The downside is a slight performance penalty. This penalty may be mitigated going forward by introducing "proxy-hints" for selected outputs.