Use mathrm by default for uppercase Latin characters

Question

I'm trying to mix Optima and AMS Euler using eulervm and mathspec in XeLaTeX. The relevant bit of code in my source file is as follows:

\usepackage{eulervm}
\usepackage{mathspec}
\setmathfont(Digits)[Numbers={Lining,Proportional}]{Optima nova LT Pro}
\setmathrm{Optima nova LT Pro}

Using this set up, Euler is used in math mode unless I specify \mathrm. For Greek and lowercase Latin characters this works out quite well, but for uppercase Latin I would very much prefer to use Optima's glyphs.

My current workaround is to stick \mathrm around every uppercase Latin variables in math mode, however this gets rather annoying after a while. Is there any way to coax XeLaTeX into using \mathrm by default only for uppercase Latin glyphs?

Answer 1

Unfortunately mathspec doesn't allow for specifying separately uppercase and lowercase letters.