Do I really need an Eddi (or similar)?

Apologies if this has been answered a million times already and happy to be directed to the relevant thread.

Is a Myenergi Eddi (or similar) solar diverter really required, or can a smart switch (obviously, with the right power rating) be retrofitted to the existing dumb tank booster and all the usual switching logic covered in NodeRed, along with some CT clamps in the right places?

Am I missing something with the capabilities of the Eddi? It admittedly looks like a nice wrapped up solution, but hardly cheap and possibly quite redundant with an existing HA setup, if I have grasped its raison d’être correctly?