@Michas: As far as I know, we can re-define our Vim's environment using the "-u" option inline with the vim command. For example:
1) Creating a file, say ~/.yourvim, with the following stuffs:
2) Then add into your ~/.bashrc file this line
alias vim="vim -u ~/.yourvim"
3) Exit the current terminal, open a new one and you can try with the new vim's environment.
I am using this trick to define my own vim. Of course we can provide more options inside the "~/.yourvim" files as well as the "alias" command. So far, it works on my Debian 8 with vim version 7.4.
There is another way: modify or create (if it does not exists)
put the following lines into the latter file
Exit the current terminal, open a new one and try. Good luck!