Spa Control Upgrade Help or Custom Order

Hello

I have an Spa Controller/ heater (Davey sp800)
Its UX design is horrible to use and there is no way to add in WiFi control.

Everything works, all the pumps/ heater / sensors/ lights. So i figured i would build a new control board with the upgrades.

The relays on the board are all 25A 250V
the power coming from the mains is 15A single phase.

I would like to have an external control panel that shows the current temp/ temp setting.
and a button to turn the blower on.
Here is the wiring diagram
I have the Pump 1A (high and low speed)

Can anyone help me with this?