-A remote master unit and several slave units is a great idea. There are many situation where you have sprinklers in different areas of a house and a single interface to handle them all would be really helpful.
-Local sensors would greatly improve accuracy and flexibility of weather adjustment.
-As for the local control, I don’t use it very much but some users may benefit of it.
When you can please upload the logging fix so I can check it. I don’t have much time but I’m interested in this project and I’ll do my best to help.
I didn’t find any other bugs, only some errors in the schematic you posted.
-SCL SDA lines are inverted on nodeMCU
-LCD PCF8574 P1 goes to LCD RW
-LCD PCF8574 P2 goes to LCD E
-LCD A1 A2 A3 should go to VCC for the default LCD address
also you should consider not using pin define that are nodeMCU specific
e.g. #define SDA_PIN 4 //D2 //:this is standard….it may be changed
so that the code will be compatible with other esp8266 modules