> best solution would indeed be support from the underlying engine
> though i'm not sure that it is a good idea to keep support for the
> original \TeX{} \input snytax at all, ie i'm not sure why one would
> like to have both
> - \input <file>         standard-version
> - \inputfile{<file>}    <file> can be a Makros or has space

But for compatibility it is necessary!
In the future, one primitve is enough.