Just discovered the amazing Raspberry Pi 3 and I am trying to learn how to use it in one of my projects.
Setup:

ASP.NET app on Azure.
RPi: 


software: Raspbian, PHP, Apache 2, and MariaDB.
has internet access and a web server a configured.

3G dongle for SMS sending, connected to the RPi.

Desired scenario:

when a specific button within the ASP app is clicked:


through jQuery $.ajax() the RPi's ip is called with the parameters phoneNumber and smsType.

then the RPi:


fetches the SMS text from a MariaDB database based on the smsType parameter.
invokes a Python script using the PHP exec("python sendSms.py -p phoneNumber -m fetchedText", $output) (i.e. with the phone number and the fetched text):


script will send the AT command(s) to the dongle.
script will return true or false based on the action of the dongle.  


echo the $output to tell the ASP what is the status.
finally, the ASP will launch a JavaScript alert() saying if it worked or not.

This is what I need to accomplish. For most of the parts I found resources and explanations. However, before starting on this path I want to understand few things:

General questions (if you think they are not appropriate, please ignore this category):

What are the (logical) pitfalls of this scenario?
What would be a simpler way to approach this?

Specific questions:

Is there a size limit to consider when passing parameters through the url?
What are the (logical) pitfalls of this scenario?
My opion would be to pass the data and the two fields (phoneNumber and SmsType) through a POST request rather then an GET request because you can send more data in an post request and encapsulate it with JSON making it easier to handle the data.
What would be a simpler approch ?
Maybe not simple but more elegant, extend the python script with something like flask and build the webserver right into the python script, saves you running a webserver with php!
Calling Raspberry Pi from ASP.NET to send a SMS remotely