I did exactly what you are saying and it works very well for me. I used 3 - 3 pole contactors that activate from 12 volts which is the only thing live in my train room prior to firing the contactors. I use a key switch on the control panel to have the ability to remove the key if needed and also I had several in the ol parts bin so the cost was nothing.

As long as the contact rating on the relays are enough for your load, you are good to go.  JP

Google the term "X-10" which is the family of carrier-current controlled switches, outlets, lamps, and other appliances. You do not need to do any extensive wiring nor do you need to use relays.

Emergency shutdown circuit for my model railroad.

Here is an example of my shutdown circuit. It uses the Westek RKK306LC.

Westek RFK100LC Wireless remote control for 120 VAC circuits

Here is another device that I use for controlling my accessory and lighting circuits on my model railroad. This device is a "wall mounted" switch that I will install in my control panel. I will have three such devices to control three different circuits. Since these are wireless I can install them in my panel and not have to connect any wiring.

Using power strips for ac connections.

I use power strips along with my wireless remotes. Since I have separate fuses on all my accessory and lighting circuits I do not need circuit breaker type power strips.

Two types of power strips are shown: with and without a built in circuit breaker.

The only reason I can think of is that two of them give 10% discounts to Veterans.

Yep, and I take advantage of that.  However, the curious "only" statement has me wondering what kind of kickback is involved.