Mix characters from various fonts (in text mode)

Question

I'm using classico as my everyday font, together with \usepackage[EULERGREEK]{sansmath}\sansmath when there are formulas. My problem is: I don't like the shape of the "equals" sign of classico. I find it much too narrow, e.g. in a \Longrightarrow, but also quite everywhere else. (MWE on pastebin)

After quite some reasearch on tex.sx (e.g. Importing a single symbol from a different font, etc) I was able to convince math mode to keep the equals sign from computer modern.

\DeclareSymbolFont{mysymbols}{T1}{cmr}{m}{n}
\DeclareMathSymbol{=}{\mathrel}{mysymbols}{`=}

I don't know if this is the right way to do it but it looks good enough to me

I'd like to change the font for the equals sign in text mode as well. Is this possible ?

I tried playing with even more things I don't understand (like catcodes, cf MWE) but could get nothing out of it.

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage[sfdefault]{classico}
\usepackage[EULERGREEK]{sansmath}\sansmath

\DeclareSymbolFont{mysymbols}{T1}{cmr}{m}{n}
\DeclareMathSymbol{=}{\mathrel}{mysymbols}{`=}

% \catcode`==13 \def ={\ensuremath{=}}

\begin{document}


\begin{center}
text: 1 2 3 = 4 5 6
\end{center}

\begin{center}
math:  $ 1 2 3 = 4 5 6$
\end{center}

\begin{center}
 arrow: $\Longrightarrow$
\end{center}

\end{document}

Answer 1

Here is a fontspec way to get the equals sign in a separate font in text mode, if you compile with LuaLaTeX or XeLaTeX.

\documentclass{article}

\usepackage{lmodern}
\renewcommand*\familydefault{\sfdefault}              % Use sans as base font

\usepackage{fontspec}
\newfontfamily{\mymathfont}{Latin Modern Math}        % Family for math symbols
\newcommand{\mymath}[1]{\bgroup\mymathfont #1\egroup} % Command to apply family
\newcommand{\EQ}{\mymath{=}}                          % Specific command for equals sign

\begin{document}
text: 1 2 3 \EQ\ 4 5 6
\end{document}