I fond the CDLatex mode in Emacs very useful. It makes typing math formulas much easier. For example `a
becomes \alpha and so on for greek letters and many other symbols. If you type equ and press Tab you get a
\beging{equation}
\end{equation}
with the cursor placed in the middle line. Similarly for "ite" (itemize), "enu" (enumerate) and so on. Typing $ gives you $$ with the cursor in between the dollar signs. and all the super and under scripts get {} automatically. You can find more info here: https://staff.fnwi.uva.nl/c.dominik/Tools/cdlatex/cdlatex.el
Anonymous
the completion is pretty much already present (Idefix/Completion/Begin{ completion)
The 'a substituion can be realized with macros.
So I don't see any necessity to cahnge something on our side ...
See also:
https://sourceforge.net/p/texstudio/wiki/Scripts/#word-completion
https://sourceforge.net/p/texstudio/wiki/Scripts/#replace-characters-by-their-latex-equivaltent-while-typing