I have tried to define a command
$\exponent$ that would look for next exponent and would put a copy of this exponent after
a, another after
b and a last one after
$\exponent^e$ would transform to
$a^e b^e c^e$.
And if this is possible, I would like
$\exponent_f$ to generate
$a^e_f b^e_f c^e_f$ and
$a_f b_f e_f$.
The difficult part is to make
$\exponent^\frac12$ be automatically replaced by
$a^\frac12 b^\frac12 c^\frac12$, but comments are suggesting that
^\frac12 is forbidden in TeX.