Is it possible to use the NodeMCU stand alone board as a Wifi Shield for the Arduino Uno?
Yes, probably (if you can load AT firmware on it), but a bit of a waste. Usual ESP for that purpose is the ESP-01 with AT firmware.
Other option if you need an Arduino for I/O reasons, try just using the ESP with Blynk code, sending commands to the Arduino with non-Blynk code… like this…
So, If i need the extra analog input on the uno, I can just send a signal to the UNO? Sorry if this sounds dumb, I’m working on my first project ^^
If you need additional analog inputs, and are unsure of your coding skills, I recommend something perhaps simpler like an addon module…
Otherwise, yes you can setup code on the Arduino to scan your analog inputs and send that info to the ESP via EasyTransfer
And remember Google is your friend 
here is another option…