If you try something like this it will show on the user-end. The 4 second delay is so that the Lookup Rule does not override the new appended values. Not sure how Laserfiche will handle it on submit though.
I'm sure that there is a better way to combine the two values as well; just threw this example out to get it started.
setTimeout(function(){
$('.myselect select').append($('<option>', {value: 1,text: 'unknown'}));
$('.myselect select').append($('<option>', {value: 2,text: 'analytical only'}));
}, 4000);
Or a combined way
setTimeout(function(){
var dataArr = [{'value':'unknown','text':'unknown'},
{'value':'analytical only','text':'analytical only'}];
// .each loops through the array
$.each(dataArr, function(i){
$('.myselect select').append($("<option></option>")
.attr("value",dataArr[i]['value'])
.text(dataArr[i]['text']));
});
}, 4000);