var formQuery = {},
              push_counters = {},
              patterns = {
                "validate": /^[a-zA-Z][a-zA-Z0-9_\.]*(?:\[(?:\d*|[a-zA-Z0-9_\.]+)\])*$/,
                "key":      /[a-zA-Z0-9_\.]+|(?=\[\])/g,
                "push":     /^$/,
                "fixed":    /^\d+$/,
                "named":    /^[a-zA-Z0-9_\.]+$/
              };

          var build = function(base, key, value){
            base[key] = value;
            return base;
          };

          var push_counter = function(key){
            if(push_counters[key] === undefined){
              push_counters[key] = 0;
            }
            return push_counters[key]++;
          };

          jQuery.each(jQuery( this ).serializeArray(), function(){

            // skip invalid keys
            if(!patterns.validate.test(this.name)){
              return;
            }

            var k,
                keys = this.name.match(patterns.key),
                merge = this.value,
                reverse_key = this.name;

            while((k = keys.pop()) !== undefined){

              // adjust reverse_key
              reverse_key = reverse_key.replace(new RegExp("\\[" + k + "\\]$"), '');

              // push
              if(k.match(patterns.push)){
                merge = build([], push_counter(reverse_key), merge);
              }

              // fixed
              else if(k.match(patterns.fixed)){
                merge = build([], k, merge);
              }

              // named
              else if(k.match(patterns.named)){
                merge = build({}, k, merge);
              }
            }

            formQuery = jQuery.extend(true, formQuery, merge);
          });

Такой скрипт правильно обрабатывает имена полей вида <select name="bool[must][0][range][tax_input.bedrooms][lte]">

Из него конечно можно залепить функцию, но мне лень…