dual console system

A lot more information is needed to give you an answer that will be realistic.
I have a system where I can have multiple DMX signals combined through an active DMX combiner to send one input to my dimmer racks while I feed DMX from a Net3 Gateway to the second input on my racks. I can also use a Gateway to take a DMX signal into my network.
This is dependent on:
What type of dimmers do you have?
Where are the consoles located?
Is there a lighting network in place?

So to answer your questions:
Yes, I have a similar type of set-up
Yes, an active DMX combiner. Doug Fleenor makes them. Or a ETCNet3 system with Gateways.
No, don't do the Y-cable.
Good luck,
John

The simplest way to do this is the old A/B switch. Fleenor make those too.

Personally I would just swap show files on the Ion. I've taught high school students to do just that.One file for the show and one, with lots of subs, for events.

The simplest way to do this is the old A/B switch. Fleenor make those too.

Personally I would just swap show files on the Ion. I've taught high school students to do just that.One file for the show and one, with lots of subs, for events.