Welcome to the Hubitat Community!
We just love to talk about device choices here. So much we sometimes skip primary questions. Yes, Hubitat Rule Machine is a very capable rule engine. The automations it can do run circles around HomeKit and Siri Shortcuts. It’s a pain to initially get HomeKit devices synced to HE, because each device, like a contact or motion sensor has to be synced with a virtual device using HomeKit automations. However once done, you just backup your Homebridge setup. It very fast and stable. This can potentially give access to very small, and very low cost sensors from Xiaomi, without the Zigbee non-compliance problem by simple joining them to the Xiaomi Aqara HomeKit Gateway.
The one limitation I have found with using Xiaomi sensors on a Xiaomi Aqara gateway through HomeKit, is with comparing two temperature or humidity sensors as a condition in an automation. HomeKit is only able to compare against a fixed value.
The HomeKit method with a Xiaomi Aqara Gateway and devices is inexpensive and easy, but it sounds like you’re no stranger to setting up these systems if you have Home Assistant experience. There’s another method that uses a specific Xiaomi Mijia gateway to get the Xiaomi sensors in HE. This is harder to get going, but should be easier once you get it setup.
Anyway, see how easily we get sidetracked on devices?! 
In short, you can do far more with HE automation, and the device capabilities that are exposed to Rule Machine allow you do much more than HomeKit is capable of. But do heed the advice to keep the Zigbee bulbs off the primary HE hub. If you want to buy another HE hub and dedicate it to bulbs only, that’s a perfectly viable method too.
I recently purchase a Mijia Mutimode Gateway to try. It supports HomeKit, and all the sensors the Aqara gateway supports, plus it is Zigbee 3.0, supports Bluetooth and Bluetooth mesh for the future when that’s more useful. Additionally, it has support for Some of the IKEA TRÅDFRI bulbs. Have not received it yet, so I don’t know the downside other than an intermittent beeping I intend to figure out or remove the beeper all together. Like the Aqara hub, it only supports 32 directly connected devices. There is a similar Aqara M2 hub releasing soon that is supposed to support up to 100 end devices, but that’s late arriving, no doubt in part due to the pandemic. Expect further delays on that.
