The wiper business can be done easily with a PLC (Programable Logic Controller). And we had an expert PLC programmer on this forum the name escapes me. Wire the logic input of PLC to the washer button of the stalk.
If the washer button is pressed less than lets say 2 seconds then PLC activates wiper once.
Else PLC activates the washer and wiper untill the washer button is released.

There should be PLCs that work on 12 V DC and cost less than $ 100.
Somebody wanted a side business, someone thke this idea and run with it.

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2010 ML350 Bluetec
2012 Mustang Convertible