choosing k elements from a "set", and concat of vecsmall

I often have a need to loop over all "n choose k" elements from a set.  The
closest builtin functionality I have found for this  is to use forsubset,
and then build a vector from that with vector as follows:

forsubset([#S,k], s0,
  my(s = vector(k, i, S[s0[i]]));
  ...
);

Is there any more appropriate/efficient way to do such a thing?  It seems a
little convoluted and odd to me that forsubset can't optionally accept a
vector as input.

Another somewhat related thing I noticed recently which feels like an
oversight is when that concat is presented with a t_VEC and t_VECSMALL, it
just inserts the t_VECSMALL as a single element.
? concat([1,2,3],Vecsmall([4,5,6]))
%12 = [1, 2, 3, Vecsmall([4, 5, 6])]
I found this out because forsubset and forperm seem to always produce
t_VECSMALL which I did not previously realize.
I realize I can work around this by wrapping the vecsmall in a call to
Vec(...) but it feels like this should not be necessary.

-Hans