I dont think the wifi problem from RF, it's might be from the modem capacity ( at least it's my case).why just not sell them and buy so you have with can port?
I'd found an used DD P4 pro for like 100€ that have CAN..
And i actually prefer using wire then wireless, after a year with Reef factory dosingpumps and some problems with wifi etc I'd feel much more comfortable with wire
And I don't think that they ever had say anything about connect dosingpump via wifi to reef master or the kh carer
Normally a standard modem can handle approx 15-20 devices connected, if it's more, some will be kicked out. My wifi problem solved by getting a modem handle 100+ devices.
Still, I have 2 x4 pro and this wont be able to use with this SPA is kind of disappointed.