My home automation, like most I expect, started growing organically before the bug really got me and I then realised that I had made mistakes along the way. 
I now go for a more architectural approach, similar to your approach above but my main recommendation is to keep it simple and have clear architectural principles. Please see my post: Smart Home Documentation & Architecture
The main complexity for me is that of Alexa. I have some devices that can't connect into Hubitat but can into Alexa (I tried GA but found it less stable and more complex - this may well have changed now but my mind works in an Alexa mode now 
) I try to have all of my automation within HE but due to the fact that some devices are not known to HE, I need to use virtual switches within HE to trigger Alexa routines. This obviously makes maintenance of automation more complex, hence my documentation post above, where I record the 'Managed' and 'Linked' systems. I strongly advise maintaining this documentation as you deploy your home automation as it's a lot easier than doing it retrospectively.
I also would recommend some naming standards for the use of HE: Please see my post at the end of this topic: Rule Machine Best Practices - #3 by UKMedia
