No, these are two completely separate networks. The SmartThings/hue bridge integration is via LAN, not Zigbee. So if a device connected to the SmartThings hub directly goes off-line, it won’t affect your Hue network at all.
LIFX is a good choice. If you do want to consider A zwave bulb, Aeotec, Domitech, and Zipato all make E27 versions.
You probably already know the following, but just to be clear: all smart bulbs are intended to be always on power, leaving it up to the bulb to decide how much current to draw. So you don’t want to have them on a regular switch. It’s OK if there’s an occasional power outage, but if you are turning the bulb on and off on a daily basis by cutting the power with a regular switch then you run a very real risk of damaging the radio inside the bulb with the inrush current each time the power is restored. This can significantly reduce the life of these expensive bulbs. So you do want to consider what kind of switch to use. See the FAQ:
I just mention that, because if the issue that you are having is people cutting current to a bulb by flipping the switch and that’s causing it to be unavailable and then messing up the repeating of your Hue network, you can get around that by using a bulb on a different protocol, but it might be worth considering changing the switch rather than the bulb so that the Bulb always remains on power and is therefore available as a repeater.