Changing Fonts between \textstyle and \scriptstyle with MTPro2

Question

I'm a fan of Spivak's MTPro2 fonts, except for the fact that the numerals don't quite match the regular Times (ptm) numerals. Is there a slick way to change the \displaystyle and \textstyle numerals to \rmdefault but keep the \scriptstyle and \scriptscriptstyle numerals? I only know an "all or nothing" approach.

Obligatory MWE:

\documentclass{article}
\renewcommand{\rmdefault}{ptm}
\usepackage[lite]{mtpro2}
\def\swap#1{\DeclareMathSymbol{#1}{7}{operators}{`#1}}
\swap1 \swap2 \swap3 \swap4 \swap5 \swap6 \swap7 \swap8 \swap9 \swap0    

\begin{document}
This 5 is nice, but is $5$? And how does $2^5$ and $5^2$ look?
\end{document}

Answer 1

It's possible, by using \mathchoice and making digits “math active”:

\documentclass{article}
\usepackage{times}
\usepackage[lite]{mtpro2}

\begingroup
\makeatletter
\newcommand{\adjustdigit}[1]{%
  \begingroup\lccode`~=`#1 \lowercase{\endgroup
    \expandafter\xdef\csname digit\romannumeral#1code\endcsname{\the\mathcode`#1\relax}
    \gdef~{\csname digit\romannumeral#1\endcsname}%
  }
  \expandafter\gdef\csname digit\romannumeral#1\endcsname{{%
    \mathchoice
      {\operator@font\mathchar\csname digit\romannumeral#1code\endcsname}%
      {\operator@font\mathchar\csname digit\romannumeral#1code\endcsname}%
      {\mathchar\csname digit\romannumeral#1code\endcsname}%
      {\mathchar\csname digit\romannumeral#1code\endcsname}%
  }}%
  \AtBeginDocument{\mathcode`#1="8000 }
}
\adjustdigit{0}\adjustdigit{1}
\adjustdigit{2}\adjustdigit{3}
\adjustdigit{4}\adjustdigit{5}
\adjustdigit{6}\adjustdigit{7}
\adjustdigit{8}\adjustdigit{9}
\endgroup

\begin{document}

This 5 is nice, but is $5$? And how does $2^5$ and $5^2$ look?

{\scriptsize 5}$\scriptstyle 5$

{\scriptsize 01234567890}

$\scriptstyle 01234567890$

$\displaystyle 01234567890$

$\textstyle 01234567890$

\end{document}

However, digits will not obey \mathit when in text or display style.