Attempting to answer my 1st question: The default TA-eStreamer input is basically a Splunk scripted input, calling the bin/splencore.sh script to talk to an FMC. That script has a hard-coded "configFilepath".
SO -- as a quick hack, if I make a copy of the "bin/splencore.sh" and modify the "configFilepath", I should be able to create a second scripted input in inputs.conf. Would that be correct?
I'm going to give it a try and report back later.