Does this work (untested)?

No.
This is what am using:

\definefontfeature[default][default][tnum=yes,lnum=yes]
\definefontfeature[mathdigits][default][mode=base,tnum=yes,lnum=yes]
\definefontfamily[mainface][serif][...]
\definefallbackfamily[mainface][math][...][preset=math:digitsnormal,features=mathdigits]
\definefontfamily[mainface][math][DejaVu Math]
\setupbodyfont[mainface,10pt]

\starttext
0123456789\par
\m{0123456789}
\stoptext

You can see the result in the attached PDF.