I am doing this for a long time now and personally I don't see the need of that complicated T-SQL code. The bacth file is the best and by far the easiest and less complicated way to execute scripts. You can also use the windows authentication with OSQL and SQLCMD using the -E switch if you want to enforce security.

In regards with the order my approach is to prefix the file names with sequence of not consecutive numbers (with gaps) like:

0010_script_1.sql

0020_xxx.sql

0030_aaa_harry_potter.sql

if you want to insert a script somewhere just add the correct prefix, if you want to change the order just change the prefix. This also gives you a visual advantage and of the obvious significance of the numbers and that the rest of the name doesn't really matter.

Another way of ensuring the execution order is maintaining an file having the script names in the wanted order. This file would be read by the batch file when executed to get the scripts in the right order. This method eliminates the need for naming or prefixing but I prefer still the prefixing method, which I find much simpler than maintaining an "order" file. I used both of them by the way.

Another thing I do I move all the executed scripts into a next deeper level folder and the output of the results an a second folder usually called _Archive and _Results. This is a way to make sure I don't execute same scripts twice. The output file is only one regardless of the number of scripts by using >> output_YYYYMMDDTHHMMSS.log syntax.