Bat file to to run a group of text files in sequence

Question

I am new here and I am having a bit of trouble obtaining my desired output.

I have a locked down system with no Powershell etc and I need to manipulate some txt files in a certain order. I have looked at doing this with excel VBA, however the time it takes to output renders this unrealistic.

I am looking to create a BAT file to complete the object via CMD.

I need it to (in this order):-

1. Change the filenames to "FILE" & 1, then 2 then 3 etc.
2. Replace all spaces with commas in the content of the text files.
3. Remove all underscores from the content of the text files.
4. Remove all Alpha text characters (A-Z) from the content of the text files.
5. Remove any blank lines from the text files.
6. Merge all text files with the filenames on EACH line of the text to for example 'output.tmp'.

I have had some luck achieving this with separate bat files however I am having trouble with points 1,3 and 4.

I would also like to at some stage be able to remove any numbers which are not between two separate values eg 1 and 3 and 6 and 9.

Any help is appreciated.

Thank you