Definitely don’t repurpose the ground wire.
Unfortunately the Aeotec micros also require a neutral, so they won’t help you unless there is someplace else on the circuit you can move them where there is a neutral.
Using a “Virtual Auxiliary”
There are some options depending on exactly what you’re trying to do. Sometimes you can replace an auxiliary switch with a battery operated switch like the Cooper RF9500. Or even the smartenIt 3 toggle.
Since the auxiliary normally doesn’t have to actually control the load to the light, you can take it off of the circuit altogether, just like you would with a handheld remote. Then the auxiliary sends a message to the hub, and the hub sends a message to the master switch. This is called a “virtual auxiliary” or a “virtual three-way.”
The Figure 8 Problem
Depending on exactly how the existing auxiliary is wired, though, you may have to do some rewiring to make sure you have both a hot and a load wire at the master switch before you can remove the aux from the circuit. In some set ups you get kind of a figure 8 situation where The existing aux is necessary to the circuit or the light won’t come on. It’s usually not complicated once you figure out exactly what’s going on, but you may need an electrician to get everything set up correctly.
Essentially, if you have a single pole switch with no auxiliary, it’s easy to replace that with a networked master as long as there’s a neutral there. Then you can add as many “virtual auxiliaries” as you like, including the battery operated ones that I mentioned.
However, once there is a nonnetworked master connected with traveler wires to a nonnetworked auxiliary, it’s not always possible to just swap things in and out or to try to ignore the auxiliary. It just depends on the exact wiring that was used. So sometimes you need to take a step back and figure out how the single pole master will work independent of the auxiliaries. And then add the virtual auxiliaries back in.
The other alternative is usually to “fish up” a neutral from somewhere else in the wall. This is discussed in the lighting FAQ.
The Lighting FAQ
Anyway, the lighting FAQ discusses various options, so it should help: