temp1 "exec darkplaces.cfg"
alias $temp1 -jump
$temp1
alias $temp1 ""
temp1 ""
Something like that might work.
You'll want "unalias exec" to be somewhere in your darkplaces.cfg somewhere though...
Interestingly, quakeworld engines don't report any errors when loading configs at start up.
qc gives greater logic and a way of easily testing what the engine is, what it supports, etc. But stuffcmding stuff to the clients every time they connect to a map is bad karma.
Alternativly, for darkplaces at least, you could exploit the fact that only two engines support menu.dat, and that its loaded on startup. Unfortunatly I'm not sure if its possible to have a null menu.
FTE supports 'if FTE isin $version then exec youarerunningfte.cfg' Which is a funky way to detect things, and I think DP supports an if command too, though probably doesn't support $version. But there's two different engines detected and distinguished :)