1 ssid would be I nice goal - but don't really see it as viable option. For starters not aware that you could mix wpa-enterprise with wpa-psk.. My trusted devices require eap-tls to get on that network, etc.
And the psk I would use that are on a isolated guest network would prob be easier then the psk I would use on my vlan psk where my iot devices go, etc.
Yeah your exactly right you can not seem to be able to assign a static IP on same ssid you do dynamic - which agree not a big deal. But would like that vlan to be different than some untagged vlan which is currently the vlan that the AP IPs and controllers sit on, etc. Once you can tag the admin vlan in unifi that whole concern does go away. And from my testing if there is no auth to the radius with the mac you just don't get anything, etc.