I understand your thinking now, but as there was no mention of possibly requiring it for any reason other than (assumedly) provisioning the controller onto the DLR network, your "might" seemed to suggest it may be required to do just that.
Using a dedicated workstation ETAP interface appliance "somewhere" in the DLR network is very common, but of course it need not be connected off of or near the controller position in the ring. But more often than not, this is where it gets fitted as it makes sense, usually, to be within eyeshot of the controller when online to it. But also, they can be installed remotely, like at an office location. I usually prefer though a Stratix solution to bridge out from the DLR, as opposed to expanding the ring segments just to give workstation access. Being a DLR, you can of course also break the network ring to temporarily connect your workstation, and if resilient, it should hold up.
Ring Supervisor is the term you're thinking of, and yes, the controller is usually the go to choice, but the Stratix switch (if there is one) can also act as Backup Supervisor, and I usually assign that as next highest precedence. But we can enable most all DLR devices to act or backup the Active Supervisor,
even the lowly ETAP. And yes, you must (should) always configure at least one Supervisor if you want to prevent potential "storms".
I'm Staff (Coordinator) so I don't work shifts, just days, normally. But a colleague who does cover technical on shift is out on maternity leave, so I offered to cover him or else others had to split the shift, and they didn't fancy it.
G.