I meanwhile (it might be a while before the feature request gets realized) cooked myself up something like this:

            var
                filters = [],
                ar, cn, ft,
                map =
                    {
                        eq: 'EQUAL',
                        dateeq: 'DATE_EQUAL',
                        neq: 'NOT_EQUAL',
                        dateneq: 'DATE_NOT_EQUAL',
                        neqornull: 'NOT_EQUAL_OR_MISSING',
                        gt: 'GREATER_THAN',
                        dategt: 'DATE_GREATER_THAN',
                        gte: 'GREATER_THAN_OR_EQUAL',
                        dategte: 'DATE_GREATER_THAN_OR_EQUAL',
                        lt: 'LESS_THAN',
                        datelt: 'DATE_LESS_THAN',
                        lte: 'LESS_THAN_OR_EQUAL',
                        datelte: 'DATE_LESS_THAN_OR_EQUAL',
                        startswith: 'STARTS_WITH',
                        doesnotstartwith: 'DOES_NOT_START_WITH',
                        contains: 'CONTAINS',
                        doesnotcontain: 'DOES_NOT_CONTAIN',
                        containsoneof: 'CONTAINS_ONE_OF',
                        containsnoneof: 'CONTAINS_NONE_OF',
                        'in' : 'EQUALS_ONE_OF',
                        notin: 'EQUALS_NONE_OF',
                        between: 'BETWEEN',
                        notbetween: 'NOT_BETWEEN',
                        memberof: 'MEMBER_OF',
                        isblank: 'MISSING',
                        isnonblank: 'NOT_MISSING',
                        hasmvvalue: 'HAS_MISSING_VALUE',
                        nomvvalue: 'DOES_NOT_HAVE_MISSING_VALUE'
                    }
            ;


            $.each( params, function( k, v ){
                ar = k.split( '~' );
                if ( ar.length == 2 ){
                    
                    ft = LABKEY.Filter.Types[map[ar[1]]];
                    cn = ar[0];

                    if ( ft && cn.substring( 0, 6 ) == 'query.' ){
                        filters.push( LABKEY.Filter.create( cn.substring( 6 ), v, ft ) );
                    }
                }
            });

Where "params" is the input I wrote of and "filters" is the output I wrote of.

I got the backwards "map" from the makeFilter() R method (had to reverse it in R) and also clean up some to remove duplicates.
By the way, there are a few discrepancies in names between R's makeFilter() method and JS Filter.js file!

Oh, something I forgot in the previous post is that a URL encoding for a filter also starts with "query." and not the column name right away as I previously erroneously wrote, so I guess that's another requirement...

Thanks.
-Leo