A more elegant solution to wiring this system?
Look at your car wiring and make the wire bundles similar. 

You can use a single larger supply (e.g. ATX PC ) and a (cheap) quad 10A 5V optoisolated Relay card.  (online everywhere)

Derate the VA on the supply because of mid-cycle surge currents or try not to switch more than one at once. 

Use twisted current pair for each source and load for EMI control.


But for source common supply another way is;

Determine load AWG cable for load power and upsize source power pair using -6 AWG smaller number gauge with an earth grounded drain wire wrapped around pair connected only at PSU source to absorb stray dI/dt from interference with high Z sensors cables.