Bypass IPFire restrictions: Edgerouter X into the DMZ (Orange) as a switch or router?

I like IPFire pretty much. I currently use green for my own devices and blue for work devices.
I would like to use blue for the originally intended purpose: WLAN and Devices that you want to restrict a bit if necessary.
Unfortunately you can’t create more zones due to limitations. I think with IPFire 3 these limitations will be removed. Unfortunately it will take some time until IPFire 3 will be available.

So I’m thinking about using the DMZ for my work devices. Does this make sense?
I still have an Edgerouter X SFP with EdgeOS (you could also install OpenWRT on the Edgerouter).

Does it make sense to put the Edgerouter X SFP in Orange?

Two considerations:
a) Edgerouter X as router with DHCP and DNS. Behind it then the work devices. The work devices are then connected to the Edgerouter. One (or more) static routes must then be entered in IPFire for the networks behind the Edgerouter.

b) Edgerouter X as switch for the Work Devices + Edgerouter X as DHCP server.

1) Which option is better?
2) Are there any other options?
3) What about QoS? I am currently quite happy with FQ_Codel. Will that still work in the above constellations?

I don’t think I can do without DHCP, since the work devices are usually configured that way and I don’t always have admin rights for them.