Have I stumped everyone with this question
There is a way. I'm on a Mac and used AppleScript calling shell scripts to accomplish the printing tasks. In FileMaker I have a preferences file that assigns printers by task. It's a long process but multiple printers (an unlimited number) can be automated.
If I understand what you are trying to do, this is fairly straightforward and you do not need to use anything outside of FileMaker scripts.
You could try setting up scripts in your database that set up the page layout and then the printer settings for each need. On each layout put a print button that links to the appropriate script. Request all of your printing using the print button and stop using the keyboard commands or menus.
Slightly more complicated is a single script that checks which layout you are on and sets page layout and printer settings as appropriate. On each layout put a button which links to the single print script.
The page layout script step will automatically set up your printing area for each printer as you would have manually selected in the Page Layout dialog. The Print script step allows you to select the actual printer and other details available in the normal print dialog.
At the end of your script reset the page layout to generic settings.
Flow of script:
Which layout am I on?
> If layout is X, Y, or Z and standard output is needed, set page layout A4 and print to Printer A
> If layout is A, B, or C and label output is needed, set page layout for labels and print to Printer B
Reset page layout to generic 8.5 x 11
Hope this helps