it would be nice to have some kind of generic attribute map to pass custom properties which could be consumed in media processing steps or in the markup builder, e.g. lazy=true
because there is currently no syntax for defining map literals in the HTL spec (see https://github.com/adobe/htl-spec/issues/63), I suggest to define a prefix for request attribute names that should be considered as media properties and retrieve them manually from request and put them into MediaArgs properties.
For example: using prefix "mediaProp:"
the MediaArgs would have properties prop1='value1' and prop2='value2'