Is it possible to launch an exe EA without metatrader?

 

The idea is multiple.

- send orders to various brokers

- faster execution (nothing heavy loaded) ?

- more reliable

Can we get the variables and functions to reach brokers servers and send requests ?

could a C++ program (for example) call these functions ?

 

In a word, no.

Where the brokers backend system is based upon MT4 Server, you must use MT4 client. The client server protocol is proprietary and unpublished.

You will find brokers who implement other backend systems and some will offer standards-based or proprieteray APIs for you to implement in a choice of languages.

CB