I have no idea about syntax, I just think it should not
be hard coded.
Maybe a new kind of configuration file ?
The content would be something like
# translation table for restriction vehicles
# vehicle used in OSM tags -> access in mkgmap
motorcar->mkgmap:car
motorcycle->mkgmap:car
bicycle->mkgmap:bicycle
...

we have a similar table in inc\access
mkgmap would use this table and ignore vehicles
which are not translated.

>
> I think "goods" should not be mapped to delivery. This might also be
> changed in the default style access rules. The wiki tells about goods:
> light commercial vehicles; e.g., goods vehicles with a maximum allowed
> mass of up to 3.5 tonnes
> So it should better be mapped to truck?

That's exactly the reason why I think it should not be hard coded.

Gerd