Welcome in the forum!
There is a program named "KitProg" that Cypress uses to program the development kits via USB using a PSoC5 chip. So what you want to do is really possible. Latest product using KitProg is the CY6CKIT-059
I try to use PSoC5 to program PSoC4 directly by dont use USB because I have "HexImage.c" and "HexImage.h" that convert from "Myproject.hex" via this app--> "AN84858\001-84858\C# Application\CY8C42xx_CY8C41xx family/Hexfileparser.exe"
Now it doesnt work I stuck in DeviceAcquire step but I dont know why.