I see your concern about cost when planning on that many controllers.
One thing I really like about Robo-Tank is that while the initial outlay for the system is not insignificant, it's far less than other controller options, and personally I've scored two complete units "used" in basically like-new condition. Although not insignificant to purchase, after that I believe Robo-Tank saves you money big time.
My ATO is driven by this 12v pump, $14 for TWO pumps, so I have a backup too; works flawlessly for me:
12v ATO pump on The Big Orange Bookstore
I set up dosing pumps in Robo-Tank for All For Reef and Carbon using these 12v pumps, which are currently unavailabe, but cost me $13 for two, and there's other, similar options; also working flawlessly for me:
12 Peristaltic Pumps on The Big Orange Bookstore
Robo-Tank is controlling my Kessil lights, including a dawn/dusk, so no additional Kessil controller needed. Robo-Tank does work with other brands of lights too, not all, but it can turn any AC device on/off on a set schedule, like a simple light timer.
Robo-Tank is backing up my InkBird heater controller for redundancy.
Robo-Tank is also able to control things like return pumps, skimmers, my UV and other devices that are either AC or DC powered. It's monitoring my pH and temp, and providing feed back on ATO and dosing container reservoir levels, and more.
I'm not cool enough (read: rich enough) for Apex gear, etc, and although not quite as polished perhaps, Robo-Tank doesn't force you to use all their expensivee, proprietary gear, from cables to "approved" pumps, etc.
Reef-Pi is as flexible as Robo-Tank and can do all of the above, but it requires much more time, knowhow and skill to get it up and running. Robo-tank is as easy as loading the software on the microSD card, firing up Robo-Tank and setting up your equipment. It's not entirely for the faint of heart, so if you like DIY and a bit of figuring, Robo-Tank would be a great option that requires significantly less DIY compared to Reef-Pi, in my experience (and I tried Reef-Pi a few years ago; couldn't get it going).
I hope this helps, let me know if you have any more questions about Robo-Tank that I can help with!