There is no reason that it shouldn't or couldn't work. Having multiple Eero's is ideal. With the latest update my network is even more stellar then before. I'm really looking forward to the updated app too.
So an update...unfortunately the Eero doesn't work with the Global Cache WF2IR and after discussing it with the Eero support desk it is as I had surmised before. The Eero router will always simultaneously emit 802.11 a/b/g/n/ac both 2.4GHZ and 5 GHZ and so with some devices that only transmit via 802.11
b which is 2.4GHZ there is an incompatibility (A head scratcher

I know!). With my TP Link WIFI router, I'm able to turn off the 5GHZ (802.11 a/n/ac band), so it only emits the 2.4GHZ (802.11
b/g band). You cannot turn on and off the different radios on the Eero unfortunately.
I've sent a request with Global Cache to
update their WF2IR to accept the other more modern 802.11 bands like ac and n.
I also updated my Eero and unfortunately the speed remains about the same. My bottleneck is the ISP as they can only provide certain max speeds living in the boonies.
Best,
Anand.