Good question. I haven't thought that far ahead yet to be honest. I may search the food science lit. tonight or tomorrow and see if there is anything that may give me some ideas for how best to proceed. If you (or any other members) have any suggestions, I'm all ears.
Jim, if you decide to do the experiment, I think you will have an answer in 1-2 days tops. How I would proceed.
Sample 1 - active established starter (AES)
Sample 2 - active new starter (ANS)
Sample 3 - ANS innoculated with small amount AES
I would first get both to similar states of activity by dumping and refeeding until both starters reach similar states of activity in similar time frames. It doesn't have to be exact. Then take half of the ANS and 1/4 or less of the AES and mix thoroughly in a new container. Now feed, and allow to get active again (or domed). Taste it and refresh again. Do at least 4 refreshes tasting it each time it becomes active after a refeeding. At least 4-5 feedings b/c this should allow you to rid most of the AES if it's not activately replicating or being over taken by the new starter.
You can note if with each feeding the flavors are leaning more towards one starter or the other, sweeter or more acidic. You can also refresh the other 2 starters (AES and ANS) alongside this experimental batch AIS (Activated Innoculated Starter) as control samples. Again 5 or more feedings is sufficient to give a strong indication if the AIS is leaning one way or the other or perhaps the 2 yeast samples will coexist peacefully.