I think this question sums it up. The answer is, I've been a ISY (and now EISY/Polisy) user for...I think over a decade. Maybe two? Is that possible? I'm more HA-curious than ready to switch over to HA completely. I just wanted to tinker, but was wondering how to do it with my existing set-up.
I'm not planning on running HA in the EISY. Actually, the opposite. My guess is, ultimately, I will end up with HA as my "master controller" where all my logic is, and where every NON-Insteon device gets managed. Then I will keep the ISY integration, since I'm familiar with it and already have an Insteon world set-up at my place. I suppose at some point, I may want to directly integrate Insteon with HA. But I do a few kinda off-the-wall things that I'm not sure HA can do. Probably can. But who knows? And it's all time intensive, so any full move to HA would probably take...well, years to be honest.
I was prompted to do this because even with the Polisy node-things, I still have a lot of smart devices that Polisy doesn't handle. My hope is that HA will be able to manage everything. Everything but Insteon. For now. If that makes sense.
I think I have enough to get started. If there is anything EISY-related that I think is helpful, I'll post back. Thank you all again. Soooo appreciated.