\setupbodyfont[lucidaot]
\setupmathrendering[lucidaot][it=]

\setupwhitespace[big]

\starttext

$x
   ^{i \leftarrow 0 = ∅}
   _{\setmathfontalternate{arrow}
     \setmathfontalternate{dotless}
     \setmathfontalternate{zero}
     i \leftarrow 0 = ∅}
$

$x
   ^{i \leftarrow 0 = ∅}
   _{\setmathfontalternate{arrow,dotless,zero}
     i \leftarrow 0 = ∅}
$

\setupmathematics[stylealternative={arrow,dotless,zero}]

$x
   ^{i \leftarrow 0 = ∅}
   _{i \leftarrow 0 = ∅}
$

\stoptext
