With regard to your statement Re: "2a. it's a REAL SYSTEM HOG. when running nodes live. and even in standby." - this is true because PCBoard is a real-time DOS application that does not work well on Windows. It does not give timeslices, and therefore the CPU goes to 100%. This problem is solved by running PCBoard in DOSBox.
I have found that NetSerial works well with PCBoard in DOSBox. NetSerial provides a better virtual modem than the one in DOSBox because the one in DOSBox does not fully support the Hayes command set. The commands for DCD (Data Carrier Detect) and DTR (Data Terminal Ready) are particularly important for a BBS.
Setting &C1 (DCD signal to indicate the true state of the remote carrier signal) and &D2 (get the modem to close an active connection and return to command mode when the DTR signal lowered) is not supported. Eg. as of DOSBox 0.74, the Status Window says the commands are unhandled:
Command sent to modem: ->AT&C1&D2<-
Modem: Unhandled command: &C1
Modem: Unhandled command: &D2
Modem response: OK
DOSBox can be configured to use NetSerial by specifying "directserial" as the device type in the DOSBox config file eg.:
I am running PCBoard 15.3/100 in DOSBox, in a Windows XP virtual machine guest, on a Windows 7 host using Oracle VirtualBox. Telnet with SyncTERM works Ok (ie. PCBoard receives an "ATA CONNECT 57600" string and properly passes the call to the BBS from its Call Waiting screen).
I have also used NetFoss, TelSrv and GameSrv successfully with other BBSes (eg. Maximus) but the problem with using them is that you lose a bit of the authentic feel of receiving carrier; especially if you want to use a frontend mailer like FrontDoor / BinkleyTerm and want the caller to "Press <ESC> twice for ..." :)
With NetSerial, each node must be dialed directly. However, the company that sells NetSerial (PC Micro) also provides other products: ModemServe and NetModem - which pool virtual modems and allows for the "node hunting" (or round-robin) you described.