Install a font set using GPO

You just have to copy the font file to the folder %systemroot%\Fonts (or, remotely, \\computername\admin$\Fonts).

To do it with a startup script, open a GPO, browse to the node Computer Configuration\Windows Settings\Scripts\Startup, and click Show Files.  A new window will open.  Copy the font files into this folder, then create a new text file with a .cmd extension.  Edit it in Notepad and enter a command such as
xcopy *.ttf "%systemroot%\fonts\" /C /H /R /Y

This would copy all .ttf files to C:\WINDOWS\Fonts, overwriting existing files with the same names.

Save the file, click Add in the Startup Properties window, and browse to the .cmd script you created.  It will then run under the local System account at startup on all affected computers.

To copy fonts on the fly you could, for example, create a list of computer names and then run a command like this:
for /F %G in (computerlist.txt) do xcopy *.ttl "\\%G\admin$\fonts\"

Replace both instances of %G with %%G if running it in a batch script.

The advantage of a startup script is that you don't have to worry about which computers are powered up and available on the network at any given time.

Yup, MSI installer worked perfectly, all machines are now updated, didn't know about that, will be having lots of fun with MSIs and GPOs I think :)