I've been designing/programming industrial controls (for the power plant industry) for the past 30 years. As mentioned when using PLC's the costs add up by adding automated valves, analog input modules, transmitters, etc. If you opt to add an HMI you have added cost of the HMI unit and associated software but gain the advantage of having more information available (status of pumps, valves, temperatures, etc.) and can have a menu system setup for different styles of beer.
What most people don't realize is the life cycle of PLC's and HMI's. By life cycle I am referring to when the manufacture no longer manufacture parts or provides support for the hardware. For HMI's the life cycle also includes the windows operating system used for windows based units as well as the programming software. PLC's typically have a 15 year life cycle and HMI's usually have a 7 year life cycle, HMI's have a shorter life cycle mainly due to the windows based hardware platform becomes obsolete which is also related to the software used to program the HMI. There are options to upgrade the HMI software, however if it doesn't support the hardware platform then you have to upgrade both.
Over the years I get involved with control upgrades for our systems but there are still a handful of relay based control systems that are still working after 75 years.
I plan on designing a control panel for my 2 BBL electric RIMS system and I am leaning on using the non-PID based controller (ezboil) since I feel that a PID controller is overkill for the home brewery application. I also plan on using old fashioned switches, lights and pushbuttons for control. I however will use a variable frequency drive (VFD) to adjust the speed of my recirc pump. This also will allow me to feed the VFD with 220V single phase power and the VFD will provide the pump the needed 3-phase power.