what is in your script? can you do it with the dos commandline?
you can create a batch job, and have a deploy job, the file copy, nsh script job and a post-install command on the last job for the windows service.
what exactly are you trying to do with your NSH script? I am sure you can translate that into a windows cmd, which can be added to the blpkg as an external cmd
The external commands in BLPackages are run in the local OS without any nsh.
You can use a batch job to first deploy the software and file using a BLPackage, and then use an nsh script to edit the file and nexec the sc start.
Alternatively, if you are adding an entry to a file, try creating a config file with properties?
Hostname = ??TARGET.NAME?? ??TARGET.CUSTOMPROPERTY??