I am attaching a patch in case anyone wants to try this proposal. A
function for ox-latex is included.

Syntax:

&[optional parameters]{contents}

With this patch, something like &foo{lorem ipsum dolor} is exported to
LaTeX as \foo{lorem ipsum dolor}.

Blocks can be nested, e.g.: &foo{lorem ipsum &bar{dolor}}.

Regarding the "optional parameters", there is nothing defined, although
I think they should be adapted to each backend. A possible use that
occurs to me:

&foo[prelatex: [lorem] postlatex: {ipsum} html: style="color:red;"]{blah blah}

This should produce in LaTeX:

\foo[lorem]{blah blah}{ipsum}

and in HTML:

<span class="foo" style="color:red;">blah blah</span>

Best regards,

Juan Manuel 

-- 
Juan Manuel Macías -- Composición tipográfica, tratamiento de datos, diseño editorial y ortotipografía