I'm not sure what you are trying to do with overridng the input_map, but if you want to stop the frontend from handling a particular action, you can do that from a plugin or layout script by adding a signal handler that returns true whenever the signal corresponding to that action is received.
https://github.com/mickelson/attract/blob/master/Layouts.md#add_signal_handlerSo for example:
fe.add_signal_handler("suppress_select");
function suppress_select( sig )
{
if ( sig == "select" ) return true;
return false;
}
will stop whatever is configured as the 'select' input from working
you could then trigger the "select" signal yourself from the script whenever you want it triggered, using
fe.signal("select");
If you just want a different key to be the "select" key, you could have a tick function that regularly checks if your select key is pressed using
fe.get_input_state()
.
https://github.com/mickelson/attract/blob/master/Layouts.md#get_input_statethose are the basics anyways of how you could approach an input override using what is there now.
hope this helps