multiple vlans on a single nic means if the nic dies I lose all my
vlans
What you are talking about is honestly no different than what most companies do with VOIP phones, where a single nic in the VOIP phone and 802.1Q tagging on the port allows for both the phone and a daisy-chained computer to share the same phy port on the switch. This is done all the time, works just fine.
security implications?
This is way too vague. What kind of security are we talking about? If the port is simply tagged on the switch then any NIC with the same tag setting could potentially connect through that port. 802.1q tagging isn't really a "security" thing, it's a segmentation thing. If you want security, look into port lockdown methods (MAC learning, etc.). Security implications are really separate from actual port/nic tagging.